JPS61289293A - Heat transfer tube and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the heat transfer tube having heat transfer surface structue, high in heat transfer coefficient and durability, and the inexpensive manufacturing method thereof by a method wherein the shape of the section of protuberance, provided in the tube, is constituted of a circle or a smooth curve like the circle at the bottom surface and an arbitrary height while the protuberances are arranged in the tube regularly along a spiral curve. CONSTITUTION:The protuberances 3 are formed on the inner wall surface 1 of the heat transfer tube along the spiral curve. The section of the protuberance 3 is circle or ellipse. When single-phase fluid, having no phase change, flows through the tube, the fluid 60 at the central portion of the tube flows into the axial direction of the tube, however, the flow direction of fluid 61, near the wall surface of the tube, is curved and a part thereof generates vertical vortex having the rotating axis thereof in the axial direction of the tube when it flows through gaps between protuberances. In the transversal section of the tube, the stream line is not curved suddenly when the flow collides against the protuberance since the protuberance is provided with a curvature, therefore, effect of corrosion due to the shear stress of the fluid may be small.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] This invention relates to the structure and manufacturing method of heat exchanger tubes used in heat exchangers such as air conditioners and refrigerators, and particularly relates to aspects suitable for single-phase flow heat exchanger tubes. This invention relates to the structure and manufacturing method thereof.

[Background of the invention]

As is well known, heat exchangers such as air conditioners and refrigerators are equipped with heat exchanger tubes, and the inner structure of these tubes includes smooth tubes without any processing, as well as U.S. Patent No. 3,768, 291
A type with two-dimensional ribs such as the one shown in U.S. Pat. A tube having a three-dimensional protruding surface structure in which a secondary side groove is added by additional machining after side ribs are provided is known.

If a heat transfer tube having this surface structure is used as a heat transfer surface for single-phase flow, for example, the protrusion shape of this surface structure is not rounded but has an acute angle. As a result, the pressure loss of the fluid increases during the heat exchanger tube's operation, and a large amount of fluid driving force is required. In addition, for a plane perpendicular to the streamline of the fluid, the fluid stagnates in that part, so the kinetic energy becomes a collision pressure, which causes the part to wear out over a long period of time. As for the heat transfer performance, the rib height and rib shape fluctuate from the optimum values due to this wear and tear, so the performance value becomes lower than the initial performance value.

In addition, in the method using this rolled plug, the secondary groove and the secondary groove must be machined, which inevitably increases the number of machining steps, which is a factor in increasing costs.

[Purpose of the invention]

The purpose of the present invention is to obtain performance with high heat transfer coefficient, and
An object of the present invention is to provide a heat transfer tube having a highly durable heat transfer surface structure and an inexpensive manufacturing method thereof.

[Summary of the invention]

A feature of this invention is that the cross-sectional shape of the protrusion provided inside the pipe is composed of a smooth curve such as a circle or an ellipse at the bottom surface and at an arbitrary height position, and such a protrusion is provided inside the pipe. They are regularly arranged along a spiral curve.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in Section 1. This will be explained with reference to FIG. A protrusion 3 is formed along a spiral curve 4 on the inner wall surface 1 of the heat exchanger tube. The protrusion 3 is a protrusion 32 having a circular plane as shown in FIG. 3(A), or an elliptical protrusion 34 as shown in FIG. 3(B). Alternatively, as shown in (C), the protrusion 36 may have an asymmetrical elliptic curve shape similar to the cross-sectional shape of an egg. Alternatively, it may be an oval form 38 as shown in (D). Further, the cross-sectional shape of the protrusion at an arbitrary height from the bottom surface has a similar shape to the bottom surface, and the cross-sectional area is smaller than that of the bottom surface. The longitudinal cross-sectional shape is shown in Figure 4 (A).
, (B), (C), and (D) are formed with smooth curves. The planes are shown in Figures 3 (A) to (D).
It may be a curved surface that approximates .

Next, the manufacturing method of the present invention will be explained with reference to the drawings.

FIG. 5 shows an example of the manufacturing method of the present invention. Inside.

A circular tube fixing tool 5 is attached along the outer circumference of the circular tube 1 with a smooth outer circumferential surface.
2 and a gear-like tool 54 are powered by an external power g.
(not shown) rotates the teeth 40 of the gear-like tool 54.
The tube is plastically deformed to form a protrusion 3 inside the tube. In this case, since the mounting angle of the gear-shaped tool determines the pitch in the tube axis o-o' direction, the shape of the protrusion 3 is similar to the tooth 4 of the tool.
Corresponding to this, the portions corresponding to the corners of the teeth 40 are rounded.

The circumferential pitch of the recesses outside the tube corresponding to the protrusions 3 is equal to the circumferential pitch of the teeth 40 provided on the gear-like tool 54, and the height of the protrusions 3 is adjusted by adjusting the amount of pressing of the tool 54. It is possible to determine the When the tool 54 is rotated in a direction perpendicular to the tube axis, rows of independent annular protrusions 3 are provided on the inner wall of the tube. When the tube 1 is fed in the direction of the arrow while rotating the gear-like tool 54 as shown in the figure, a spiral row of protrusions is formed. Even if the tube 1 is fixed and the gear-shaped tool 54 is advanced in a spiral manner, a series of protrusions that advance in a spiral manner are formed. Note that, generally, the tube is fed in the axial direction and the tool 54 is fixed in order to manufacture the tube.

A flat surface remains between the rows of protrusions.

It is not possible to perform fine processing to promote boiling and condensation outside the tube in the concave portion created when providing the protrusion 3 outside the tube.
The smooth part outside the tube excluding this part becomes the effective area for promoting heat transfer outside the tube. Therefore, in order to perform external machining with high precision, a surface parallel to the tube axis is required on the outside of the tube between each row of protrusions. At this time, if the tube outer surface is parallel to the tube axis, the tube inner surface is also parallel to the tube axis in this portion.

FIG. 5A shows a schematic diagram of a gear-like tool 54. By changing the circumferential angle β of the tooth tip of the tool, the pitch Z in the circumferential direction of the projections can be changed, and the tooth tip height h is Use one that is larger than the depth of pushing into the pipe from outside the pipe. To give an example of this gear-shaped tool 54, the outer diameter is 33~
35mm, the height h of the tooth tip is 0.45~0.8am, the circumferential angle β of the tooth tip is 10''~20°, the width W of the tooth tip is approximately 1m, and by using a gear-shaped tool with these dimensions, the rib height can be reduced. Sae=0
．． Heat exchanger tubes with a diameter of 45 to 6 m and a circumferential pitch Z of 2.5 to 5 m can be manufactured.

In this case, if the outer radius changes, the tooth tip circumferential angle β that forms the optimum circumferential pitch changes accordingly.

The rib pitch in the tube axis direction can be changed in the range of 5 to 14 aa by tilting the gear-like tool 54 by 5 degrees to 20 degrees, assuming that the angle of the gear-like tool 54 is 0 degrees in the direction perpendicular to the tube axis.

Although the figure shows a diagram in which one row of protrusions is formed using one tool 54, it is also possible to form a plurality of rows of protrusions by lining up a plurality of tools 54.

These selections can reduce the number of man-hours based on the formation of the protrusion rows, but are determined by the correlation between the pitch of the protrusions in the circumferential direction and the pitch of the protrusion rows in the tube axis direction. By such a method, the cross-sectional shape of the protrusion 3 has an arc shape, and the longitudinal cross-sectional shape of the protrusion 3 cut in the direction of the protrusion row has arc-like undulations in the longitudinal direction of the protrusion row. A row of protrusions in the shape of a protrusion can be formed on the inner wall of the tube.

As an example of the size of the protrusions, it is best to use an ellipse with a long axis of 2 to 5 m and a short axis of 1.5 to 3 mm.As shown in the figure, each row of protrusions is independent and has a conical shape with a rounded tip. The structure may be such that the protrusions are arranged on the inner wall surface, or the adjacent protrusions in the same row of protrusions may be more undulating than the smooth part of the inner wall of the tube.

FIG. 6 shows a schematic diagram of streamlines when a single-phase fluid with no phase change flows inside the tube.The fluid 60 in the center of the tube flows in the direction of the winding axis, but the fluid 61 near the wall surface The flow direction is bent by the protrusions, and when a portion of the flow flows out through the gap between the protrusions, a longitudinal vortex is created whose rotation axis is in the direction of the tube axis.

As shown in FIG. 7, the protrusions of the heat exchanger tube of the present invention have a curvature in the longitudinal section even when the flow collides with the protrusions, so that the streamlines do not curve sharply , the shear stress caused by the viscous force of the fluid acting on the wall surface is smaller, and the erosion effect caused by the fluid shear stress is smaller. Since the flow passing through the side surface of the protrusion also has a curvature, there are few rapid changes in the direction of streamlines and the generation of separation vortices, and the effect of erosion due to the action of fluid force is negligible.

In order to confirm the corrosion resistance, an accelerated corrosion experiment was conducted under the conditions shown in Table 1.

Table 1 Corrosion Experiment Conditions As shown in Table 2, the experimental results show that the corrosion rate of the round protrusions is slower than that of the three-dimensional protrusions that are rectangular. This is almost the same as the corrosion rate of conventionally used heat exchanger tubes with two-dimensional protrusions that have been confirmed to have corrosion resistance, and the three-dimensional shape with round protrusions shown here is not practical. There is no degree of corrosion.

The performance of the heat exchanger tube having three-dimensional protrusions with curvature according to the present invention will be described below.Among the parameters that affect the performance of the heat exchanger tube of the present invention, the protrusion height, the protrusion pitch in the circumferential direction, and the protrusion pitch in the tube axis direction. We focused on the pitch of the protrusions and conducted experiments to clarify its effect. The heat exchanger tube inner diameter d is 14.
Experiments were conducted in the range of 7 m to 15.81 m.

In FIG. 9, the pitch p in the tube axis direction is fixed as 711II,
Further, the pitch 2 in the circumferential direction is fixed at 41, and the protrusion height e is o, 4sm (C> mark), 0.5m (Δ mark).

The horizontal axis shows the measurement results of the heat transfer coefficient and pressure drop when changing to 0.6 m (0 mark).The horizontal axis shows the Reynolds number (=u-d
/υ, u: Average flow velocity in the pipe (m/s).

d: Pipe inner diameter (I), υ: Fluid kinematic viscosity coefficient (m2/S)
), and the vertical axis is the dimensionless heat transfer coefficient Nu/Pr” (
=αd/λ/Pr″4.a: Heat transfer coefficient (W/m”・K
), λ: thermal conductivity of the fluid (W/m·K), Pr: Prandtl number of the fluid), and resistance coefficient f of the pipe.

Although it is not shown in Fig. 9 to avoid clutter, we conducted an experiment on a smooth tube without any processing on the inner surface, and found that the heat transfer coefficient was not shown in the conventionally known information. It is in good agreement with the Dittus -30elter equation, Nu = 0.023Rall'P r'' (graph A), and the resistance coefficient of the pipe is Pra
ndtl formula 1/”Y7=2.OQog (Re 1
7) -0,8 (Graph B) Results are obtained that are in good agreement. Note that the inner diameter of the pipe is 15.8 m in this case.

Regarding the heat transfer coefficient, those with protrusion heights of 0.5 m and 0.6 m have a performance that is more than twice as high as that of the smooth tube (A).

As shown in FIG. 10, as the protrusion height e increases, the rate of increase in the resistance coefficient becomes higher than the rate of increase in the heat transfer coefficient.

As shown in FIG. 9, increasing the height of the protrusion increases the pressure loss, and when the pressure loss increases beyond a certain limit, it becomes impossible to absorb the reduction in pressure loss due to the increase in heat transfer coefficient. In other words, in this case, when the protrusion height becomes higher than 0.5 m, the resistance coefficient increases even though the increase in heat transfer coefficient is small, so the heat transfer promotion effect decreases, and the protrusion height increases. It is considered that 0.5 kaku is the optimum height.

To confirm this, the results obtained in FIG.
, G. Eckert “Application of
RoughSurfaces to eat
Exchanger Design”.

International Journal of
Heat and Mass Transfer, Vo
A, 15. p1647-p1658.1972)
Regarding the heat transfer coefficient and resistance coefficient given by (3t/s t,) Cf/f, ) 113 (subscript 0: smooth tube), The evaluation was made based on the ratio of these to a smooth tube that had not undergone any such processing. These values are 1 for smooth tubes.
The value increases as the heat transfer performance improves, and the experimental value shown in Figure 9 above is changed to a water velocity of 2.5 m/
s and the physical property values corresponding to the water temperature of the refrigerator to which this heat exchanger tube is applied. The results are summarized in FIG. 10 for the case of Re=3X10'.

As shown in Figure 10, the heat transfer tube with the best heat transfer performance has a protrusion height of 0.5, and the protrusion height is 0.5 +
When it becomes higher than m or lower than 0.5 m, the heat transfer performance shows a low value.

This optimum height of the protrusion is related to the boundary layer near the wall of the fluid, and although the value varies somewhat depending on the pipe diameter, etc., the optimum height of the protrusion is considered to be a constant value. A conventional two-dimensional ribbed tube (U.S. Patent No. 3
, 768, 291) experimental data (e = 0.3 m
, p = 4 mm), the equation (1) indicating the heat transfer performance is calculated as 1.43, and if the range higher than this value is defined as the range having the characteristics of a three-dimensional ribbed tube, then the range of protrusion height is 0. It will be .45 to 0.6 mm.

Next, we will discuss the results of a model experiment investigating the effect of the circumferential pitch of the protrusions on heat transfer performance.

In this case, 2 is the circumferential pitch of the protrusions on the inner surface of the tube.

Figure 11 shows the measurement results of the heat transfer coefficient and resistance coefficient when the pitch p in the tube axis direction is fixed at 7 m and the protrusion height is set at 0.45 m, and when 2 is varied. 2 is 2
．． The results are shown for 5m (X mark), 4■ (0 mark), and 5m (O mark).

Comparing the results of z = 2.5sn and 4 cabinets, the heat transfer coefficient shows a high value for z = 4 cabinets, and the resistance coefficient f is z = 2
．． Since 5 m is larger, it is clear that 2=4 am has higher heat transfer performance.

In the case of z=2.5+m, the protrusions 5 are continuous as shown in FIG. 12, and there is no gap C between the protrusions, and there is a gap between the protrusions as shown in FIG. 13. The longitudinal vortex 6 generated from the vortex 6 is small in size, and a minute longitudinal vortex 7 is emitted. In other words, a two-dimensional protrusion is the extreme density of protrusions, and the heat transfer promotion mechanism approaches the secondary protrusion from the three-dimensional protrusion, so the heat transfer performance becomes similar to that of the two-dimensional protrusion.

Figure 11 shows the two-dimensional protrusion (◇ mark y p=7m, e=0.5
The measurement results of m) are shown together with the results of three-dimensional protrusions.

As shown from this result, when the pitch 2 becomes denser, the pressure loss becomes higher, similar to the result of the resistance coefficient of the two-dimensional protrusion.

In the case of z=4■, as shown in Figure 13 (b),
A longitudinal vortex 6 having a rotation axis in the flow direction is generated from the gap C between the protrusions, and this enhances the heat transfer promoting effect. The flow that passes through the two-dimensional protrusion separates at the position of the object,
Heat transfer is promoted by redeposition of the flow at the trailing edge of the object. In this case, the flow stagnates immediately after the object, increasing pressure loss, but in the case of three-dimensional protrusions, heat transfer is promoted by the longitudinal vortex, so the energy of the flow can be effectively used to promote heat transfer. Can be used. In this case, the gap C of the test heat exchanger tube was 11, and the distance in the longitudinal direction of the protrusions was 3. If this gap C becomes larger than a certain extent, longitudinal vortices that are effective in promoting heat transfer will not be generated, and the effect of promoting heat transfer will not be very high.As shown in Figure 11, when the circumferential pitch 2 is 5 m In the case (marked 0), the increase in the heat transfer coefficient is lower than in the case of z=4m, which confirms that the heat transfer coefficient decreases as the gap C becomes wider.

In this case as well, as mentioned above, the experimental values are organized using the formula that generally expresses heat transfer performance, s t/ s t0/ (f/ Je) i/3, as shown in Figure 1 shown in Figure 14. The maximum value is taken at z=4m. Furthermore, the value of D was obtained from experimental values for a two-dimensional rib (s=0.3++a, p=4■), indicating that the three-dimensional protrusion has a high heat transfer promoting effect. As mentioned above, if the range is defined as a range higher than the value calculated from the experimental data of the two-dimensional ribbed heat exchanger tube, the pitch range in the circumferential direction is 3.5 m to 5 m.
It is.

Regarding the influence of the axial pitch, as shown in Fig. 15, when the rib height a = 0, 5 ms, and the circumferential pitch z = 4 m, the pitch in the tube axis direction is 5 m, 7 ms.
An experiment was conducted for the case of m+10 mm.

In Figure 15, the pitch in the tube axis direction is 5m5 (mark), 7■ (Δ
(marked) and 10 mm (marked 0), the closer the axial pitch is, the higher the heat transfer coefficient and pressure loss are. These experimental values were also organized using the ratio of heat transfer coefficient to resistance coefficient (st/5ta)/Cf/f, )''/3 as shown in Figure 16. Pitch 5 pus and 7 kaku show almost the same value, but pitch 1
The experimental values for 0aw are considerably lower than those for 5mm and 7++m. As shown in FIG.
A vortex is generated in the three-dimensional protrusion portion 3, and the vortex is effectively used to promote heat transfer, and when the next downstream protrusion exists within the distance of diffusion, high performance is maintained. This case is shown in Fig. 17(a), and the distance over which the vortex spreads is
If the protrusion has a two-dimensional shape, it is approximately 10 times the height of the protrusion, and if the rib height is 0.5 mm, then u = o, 5 mm x 1
0=5m, and the part indicated by n in Figure 17 is approximately 5m.
In other words, when the axial pitch is 5m and 71, the performance maintains a high value, but when the axial pitch is 1101
In the case of I, as shown in FIG. 17(b), p >
In the case of Q, the axial pitch is longer than the vortex diffusion distance, so there are many smooth areas where vortices are not generated.
The heat transfer promotion effect is reduced. As mentioned above, if the value is higher than the ratio of the heat transfer coefficient and pressure loss calculated from the experimental data of the two-dimensional ribbed heat exchanger tube (Fig. 16, D) and is within a practical range that is easy to manufacture, the tube The axial pitch range is from 5a++ to 9■.

As a result of experimental consideration of each dimension of the protrusion, the height range of the protrusion on the inner surface of the tube is 0.45cm to 0.6cm.
The optimum dimensions were a protrusion row with a circumferential pitch of 3.5 m to 5 m and an axial pitch of 5 m to 9 cm.

Note that the flow that passes through the rows of rounded protrusions formed on the inside of the tube differs depending on their arrangement. The flow shown in FIG. 18 shows a flow pattern when the protrusions 3 are arranged in a staggered manner, and the flow 90 of the protrusions re-collides with the protrusions in the trailing portion, thereby promoting the heat transfer effect. However, as shown in FIG. 19, when the base-like protrusions 3 are arranged, the vortices in the wake of the protrusions 100 collide with the protrusions again before being diffused, and the heat transfer is sufficiently promoted. Also, the flow outside the protrusion is in a straight line in the direction of the tube axis.

Since heat transfer is not promoted, heat transfer performance is higher if the arrangement is staggered rather than in a base shape.

On the other hand, a conventionally used so-called two-dimensional ribbed tube having continuous corrugated projections has a high heat transfer performance as shown in FIG. 11, but has a significantly high pressure loss. If the pressure loss is too high, a large amount of pump power will be consumed to circulate the same fluid, so the lower the pressure loss, the better.

In the case of the heat transfer tube of the present invention, due to the increase in the heat transfer coefficient, the required heat transfer area is smaller for the same heat load, and the pressure loss is reduced by that amount, so the increase in the resistance coefficient can be sufficiently absorbed. can do.

Furthermore, since the generation of turbulent vortices near the tube wall is not significantly influenced by the tube inner diameter, the applicable range of the heat exchanger tube having this three-dimensional protrusion is IQ ~ 25.41.

A heat transfer surface structure can also be provided on the outer surface of the heat transfer tube of the present invention described above. The method is described below. First, protrusions are formed on the inner surface of the heat exchanger tube.

When ribs are formed inside a heat transfer tube by roll processing from outside the tube, it is not possible to form a microfabricated heat transfer surface structure in that part.
Since the effective area increases, the structure of the heat transfer tube requires forming a concave part by rolling on the outside of the tube, and realizing a heat transfer promoting surface structure on a surface highly parallel to the tube axis. Therefore, in the next step, as shown in FIG. 20, a smooth part 207 outside the tube, that is, a part where a concave part is not formed when forming a protrusion, has a porous heat transfer surface structure 2 that is effective for boiling heat transfer.
08 will be provided. Note that 230 is a recess formed when the protrusion 3 is provided.

In this case, micro-machining on the outside of the tube to improve the heat transfer coefficient outside the tube may be performed first, and then roll processing may be performed to form ribs on the inside of the tube. Depending on the structure of the tool, the previously formed external heat transfer promoting surface structure may be destroyed, so we will explain here the case where the internal processing is performed first to form the internal ribs, and then the external micromachining is performed. do.

As an example, first, a shallow groove (0.1 to 0.2 mm) is formed in a direction of approximately 45 degrees to the tube axis by knurling.6 Next, a cutting process is performed using a cutting tool at approximately right angles to the tube axis. is performed to form the fins 212. Appropriately, the height of the fins is approximately 1 cm, and the pitch is approximately 0.4 to 0.6 m. By doing this, it is possible to cause the sawtooth fins to lie down or to crush the fins by rolling, etc. in a zero-order process in which rows of sawtooth fins are provided on a smooth surface before processing. The method allows adjacent fins to be joined together to form a porous structure 208 having cavities 209 and apertures 210 under the skin of the heat transfer surface. Figure 21 shows the appearance of the heat exchanger tube.

For example, let us consider a case where water is flowed into the inside of such a heat transfer tube and Freon refrigerant, which is a low boiling point organic medium, is flowed outside the tube. Shell-tube heat exchangers, in which multiple heat transfer tubes are inserted into cavities, are widely used in evaporators of turbo refrigerators, etc. Typically, the temperature of the water inside the tube is about 5 to 10 degrees Celsius higher than the temperature of the Freon refrigerant outside the tube. Due to the presence of the protrusions, the flow within the tube generates turbulence near the wall surface, and heat exchange between the inner wall of the tube and the main flow of the flow within the tube is more active than in the case of a smooth surface.

On the other hand, in heat exchange between the outer wall of the tube and the Freon liquid refrigerant on the outside of the tube, once boiling occurs, vapor bubbles are retained within the cavity, and a thin Freon liquid film is formed between the inner wall of the cavity and the vapor bubbles. The evaporation of this thin liquid film promotes latent heat transport based on the evaporation of the liquid.

Figure 22 shows the embodiment shown in Figure 21 with a protrusion height of 0.3.
Taking the case of as as an example, there is an optimal range of the protrusion pitch P in which high heat transfer efficiency can be obtained, as can be seen from Figure 0, which shows the influence of the protrusion pitch P on the heat transfer efficiency of the heat transfer tube. That is, when P is large, the area of the smooth portion on the outside of the tube becomes large, and the heat transfer area forming the porous structure can be widened by machining effective for boiling heat transfer. Therefore, the heat transfer efficiency on the outside of the tube is improved by the increase in area.

On the other hand, as P increases, the heat transfer coefficient on the inside of the tube suddenly increases, as shown in FIG. Heat transfer efficiency decreases. In this case, the rate of decrease in heat transfer performance due to forced convection on the inside of the tube is greater than the rate of improvement in boiling performance on the outside of the tube, and therefore the overall heat transfer efficiency of the heat transfer tube decreases rapidly as P increases. When the zero-order P is small, the heat transfer surface area affected by turbulence does not increase even if it is made smaller than a certain level, so the heat transfer efficiency of forced convection in the tube hardly changes.

On the other hand, as P becomes smaller on the outside of the tube, the ratio of the area occupied by the outside of the tube to the area of the entire outside of the tube rapidly decreases, so that the boiling heat transfer performance outside the tube also decreases rapidly. Therefore, due to the phenomenon of 1 or more in which the overall heat transfer efficiency of a heat transfer tube decreases rapidly even when P becomes small, there is an optimal range of protrusion pitch P that maintains a high overall heat transfer efficiency of the heat transfer tube. I will do it. From FIG. 22, the optimum range for the heat transfer coefficient of the heat transfer tube is 5 m to 15 m.

By the way, when constructing a shell-tube heat exchanger using the heat exchanger tube of the present invention, as shown in No. 24@, both ends 215 of the heat exchanger tube are widened, and after the protrusion forming process is performed,
A method can be used in which the heat exchanger tubes are inserted into the tube sheet 216 and the tube sheet and the heat exchange tubes are joined by tube expansion or the like. The method of creating protrusions inside the pipe by conventional plug processing or drawing processing is as follows:
Since it is impossible to process the heat exchanger tube unless both ends are straight, the protrusions on the inside of the tube are first processed, and then the protrusions at both ends are cut to make a smooth surface before expansion.

Therefore, when the heat exchanger tube according to the present invention constitutes a shell-tube heat exchanger, it is possible to reduce the assembly process.

〔Effect of the invention〕

According to the present invention, a heat exchanger tube with high heat transfer coefficient and high durability can be obtained, and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a heat exchanger tube according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view of the main part showing the structure of the heat exchanger tube of the present invention, and FIGS. 3(A), (B), ( C). (D) is a plan view showing another embodiment of the present invention, and FIGS. 4(A), (B), (C), and (D) are respectively (A) of FIG.
, (B), (c), (D) cross-sectional views, Figures 5 and 5.
Figure A is a diagram showing an example of the manufacturing method of the present invention, Figure 6 is a detailed explanatory diagram of the present invention, Figure 7 is a cross-sectional view of the heat exchanger tube of the present invention, Figure 8 is a front view of the same, Figure 9 ~Figures 11 and 14~1
FIG. 7 is a diagram showing an example of experimental data of the present invention, FIGS. 12, 13, 18, and 19 are diagrams showing the relationship between protrusion pitch and heat transfer efficiency, and FIGS. A diagram showing an example of a heat exchanger tube to which the present invention is applied, FIGS. 22 to 23 are diagrams explaining the performance of the embodiment of FIG. 20, and FIG.
It is a figure which shows the example of a use of the Example of a figure. DESCRIPTION OF SYMBOLS 1... Heat exchanger tube, 3... Protrusion, 40... Teeth, 52...
... Circular tube solidity No. 1 Figure z z Figure A 3 Figure < A) (B) Meat 4 Figure (A) (B) ゛F2, l
Tundu Hongke 5 figure ¥: J q Turning Inorian number Shake Toku /θ Figure ρ4 ρ, 5 ρ・6 tut fF
L height 1 CC range -) No. 11 Fig. Inol number Re 12 Fig.'￥J ノ3 Fig. 74 Fig. Circumferential width 2 (take??t) 'f, 15 Fig. Inol spa number Re K /8 Figures, wo 矧 Z77 Figure ¥ JZ1 Figure vZZ Figure Ml Directions (gy art) Tomi 23 Figure 24 Figure

Claims (3)

[Claims] 1. The inner surface of the heat exchanger tube has a row of protrusions intermittently provided at regular intervals along one or more spiral curves, and the inner surface of the tube between each row of protrusions has a plane parallel to the tube axis. in which each of the protrusions has a height of 0.45 mm to 0.
．． 6 mm, the circumferential pitch is 3.5 to 5 mm, the cross-sectional shape at the bottom and any height is a circle, ellipse, or a smooth curve similar to these, and the cross-sectional area is continuous in the height direction of the protrusion. A heat exchanger tube characterized by a reduction in temperature. 2. The inner surface of the heat exchanger tube has a row of protrusions intermittently provided at regular intervals along one or more spiral curves, and the inner surface of the tube between each row of protrusions has a plane parallel to the tube axis. have,
In a heat transfer tube having a porous heat transfer surface on the outer surface, each of the projections has a height of 0.45 mm to 0.6 mm, a circumferential pitch of 3.5 mm to 5 mm, and an axial pitch of 5 mm to 1.
5 mm, and the cross-sectional shape of each protrusion at the bottom and at any height is a circle, an ellipse, or a smooth curved line approximating these, and the cross-sectional area decreases continuously in the height direction of the protrusion. heat exchanger tube. 3. In the case where the inner surface of the heat exchanger tube is provided with a row of protrusions intermittently at constant intervals along one or more spiral curves along a surface parallel to the tube axis by plastic working, the protrusion is intermittently formed on the outer periphery. By extruding from the outside of the tube into the inside of the tube using a gear-shaped tool and a circular tube fixing tool,
A method for manufacturing a heat exchanger tube, characterized by forming intermittent rows of protrusions on the inner surface of the tube.