JPH0579918B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a heat exchanger and a method for manufacturing the same. The present invention relates to a heat exchanger that is optimal for improving heat exchange performance, particularly in a heat exchanger in which separate heat transfer tubes are spirally wound around the inner periphery of a double-walled tube, and a manufacturing method thereof.

[Background of the invention]

Generally, heat exchangers such as air conditioners and refrigerators are equipped with heat transfer tubes, and the inner structure of these tubes may be smooth tubes without any processing, or the
- As in the example described in Publication No. 31863, the first rib was created by inserting a processing plug for rolling into the inside of the pipe wall and performing groove machining, and then the second groove was created by additional machining. A tube with a three-dimensional surface structure is used.

If a heat exchanger tube having this surface structure is used for a heat exchanger tube of a type in which the heat exchanger tube is wound spirally around the outer surface of the inner tube between double tubes, for example,
The protrusion shape of this surface structure is not rounded but has an acute angular shape, and as will be explained in detail later, the flow that turns the corner creates a separation vortex, which increases the pressure loss of the fluid between the inlet and the outlet of the heat transfer tube, and drives the fluid. A lot of force is required. In addition, with respect to a plane perpendicular to the streamline of the fluid, the fluid stagnates in that part, so kinetic energy becomes collision pressure, and therefore that part is worn 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, this method using a rolled plug requires machining the primary groove and the secondary groove, which inevitably increases the number of machining steps, which is a factor in increasing costs.

Furthermore, although it is possible to form protrusions on the inner surface of the heat transfer tube with this rolled plug method, processing is required to form a convex-concave structure on the outer surface of the tube to further enhance heat transfer. for,
Since a process different from the process using the rolled plug is required, there was a problem of increased costs.

[Purpose of the invention]

The present invention has been made in order to solve the problems of the prior art described above, and is made by forming intermittent recesses along a spiral curve on the outer surface of a heat transfer tube that is wrapped around the outer circumference of the inner tube of a double tube. In addition to increasing the heat transfer area outside the tube and adding turbulence to the fluid flowing outside the heat transfer tube to promote heat transfer, a continuous circular or elliptical shape with a protrusion on the inside of the tube with curvature on the sides is provided. The object of the present invention is to provide a heat exchanger in which protrusions are provided to induce turbulence in the fluid and to obtain high heat transfer performance, and a method for manufacturing the same.

[Summary of the invention]

The structure of the heat exchanger according to the present invention is a heat exchanger in which a separate heat transfer tube is spirally wound around the outer periphery of the inner tube of the double tube. A heat exchanger tube to be wound around the heat exchanger tube is provided with a row of recesses intermittently on the outer surface of the tube along at least one spiral curve formed on the outer surface of the heat exchanger tube,
As the depression is formed, a row of protrusions are formed on the inner surface of the tube whose cross-sectional shape at the bottom and at any height is circular, elliptical, or an asymmetrical elliptical curve, and whose cross-sectional area decreases in the height direction. This is a heat exchanger tube made of aluminum.

Further, a method for manufacturing a heat exchanger according to the present invention is a method for manufacturing a heat exchanger in which a separate heat transfer tube is wound spirally around the outer periphery of an inner tube of a double tube. The heat exchanger tube to be wrapped around the outer circumference of the inner tube is first rolled along at least one spiral curve while pressing a gear-shaped roll having an arcuate or rectangular protrusion at the tip against the outer surface of the heat exchanger tube. By rolling with the heat exchanger tube, a row of intermittent depressions is formed on the outer surface of the heat exchanger tube, and as the depressions are formed, a circular cross-sectional shape at the bottom and at a given height is formed on the inner surface of the tube. After processing the heat exchanger tube to form a row of protrusions that have an elliptical shape or an asymmetrical elliptic curve and whose cross-sectional area decreases in the height direction, the processed heat transfer tube is used as the inner tube of the double tube. This is a method of wrapping it spirally around the outer circumference.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 7.

First, FIG. 1 is a partial cross-sectional perspective view showing the structure of a heat exchanger according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional perspective view showing details of the heat exchanger tube portion of FIG. 1, and FIG. Figures a, b, and c are front views showing the shape of the protrusions formed on the inner surface of the heat exchanger tube shown in Figure 2, and Figure 4.
a', b', c' are respectively a, b, cnA-
They are sectional views taken along the lines A', B-B', and C-C'.

The heat exchanger shown in Fig. 1 is used, for example, in absorption water heaters, air conditioners, chemical plants, etc. 1 is the outer pipe of the double pipe, and 2 is the inner pipe of the double pipe. Tube 3 indicates a heat transfer tube wound helically around the outer periphery of tube 2 inside the double tube.

As shown in FIG. 2, the heat exchanger tube 3 has a row of recesses 5 formed intermittently at regular intervals along at least one spiral curve 4 formed on the outer surface of the tube. Along with the formation of the tube, a row of protrusions 6 with smooth surfaces are formed on the inner surface of the tube separated by the tube wall.

The projection 6 may have a circular front view as shown in FIG. 3a, an elliptical projection as shown in FIG. 3b, or an oval cross section as shown in c. It has an asymmetrical elliptic curve shape 6c similar to .

Further, the cross-sectional shapes of the portions higher than the bottom surface of the protrusion 6 are similar to the bottom surface, and their cross-sectional areas are smaller than the bottom area in the height direction of the protrusion. Further, the cross-sectional shape is not formed by sharp lines with acute angles that distinguish the sides of the ribs, but is formed by curved lines as shown in FIGS. 3a, b, and c.

The rows of depressions 5 formed on the outer surface of the tube are shown in Fig. 4.
Any shape can be considered, such as a rectangular parallelepiped-shaped recess 5a as shown in a', a U-shaped recess 5b as shown in a and b, or an asymmetrical recess 5c as shown in c'. The shape of the protrusion 6 on the inner surface of the tube is determined depending on the shape of the recess 5.

A heat exchanger tube 3 having such a row of recesses 5 on the outer surface of the tube and a row of protrusions 6 on the inner surface of the tube is wound spirally around the outer circumference of the tube 2 inside the double tube as shown in FIG. A heat exchanger is configured.

In this heat exchanger, a fluid flows inside a heat transfer tube 3 wrapped around the outer periphery of a tube 2 inside the double tube, and a fluid flows through a gap 7 of the double tube narrowed by the wrapped heat transfer tube 3. Heat exchange occurs between fluids.

The heat exchanger tube 3 shown in FIG. 2 can be easily manufactured by the method described below.

FIG. 5 is an explanatory diagram showing a method of processing a heat exchanger tube according to an embodiment of the present invention.

As shown in FIG. 5, a gear-shaped roll 10 having an arcuate or rectangular protrusion 11 at the tip is pressed against the outer surface of the heat transfer tube 3 and rolled while pressing along at least one spiral curve. By doing so, a row of intermittent depressions 5 is formed on the outer surface of the tube.

The circumferential pitch of the row of recesses 5 is determined by the circumferential pitch of the protrusions 11 corresponding to teeth provided on the gear-shaped roll 10, and the depth of the recesses 5 is determined by the amount of pressing of the roll 10. It can be determined by adjusting.

Along with the formation of these recesses 5, protrusions 6 are formed on the inner surface of the tube, and the pitch and height of the protrusions in the circumferential direction are determined.

Note that when the roll 10 is rotated in a direction perpendicular to the tube axis, independent rows of recesses and protrusions can be formed on the outside of the tube and on the inner surface of the tube.

When the roll 10 is advanced in a spiral as shown in FIG. 5, depressions on the outer surface of the tube and rows of protrusions on the inner surface of the tube are formed along the spiral curve. It goes without saying that forming the recesses and protrusions along the spiral curve is more advantageous in terms of reducing the number of man-hours.

Furthermore, although FIG. 5 shows an example in which one roll 10 is used to form a row of recesses and protrusions along a single spiral curve, a plurality of rolls 10 are lined up to form a row of multiple spiral curves. It is also possible to form rows of parallel depressions and projections.

By such a method, the protrusion 6 has a recess 5 on the outer surface of the tube, the cross-sectional shape of the protrusion 6 based on the recess 5 is an arc shape, and the longitudinal cross-sectional shape of the protrusion 6 cut in the direction of the row of protrusions is as follows. A protrusion row can be formed on the inner surface of the tube in the shape of a protrusion that has arcuate undulations in the longitudinal direction of the protrusion row.

As described above, these processes can be easily carried out by pressing a roll with gear-shaped protrusions from outside the heat exchanger tube, which has an excellent effect in reducing the number of manufacturing steps.

The heat exchanger tube 3 processed by the method shown in FIG. 5 is wound helically around the outer periphery of the inner tube 2 of the double tube shown in FIG. 1 to complete the manufacture of the heat exchanger.

According to the heat exchanger of this embodiment, the heat transfer performance of the fluid flowing through the gap 7 of the double tubes is improved, the cross-sectional area of the flow path changes due to the spirally wound heat transfer tubes 3, and the flow is disturbed. The recesses 5 on the outer surface of the heat exchanger tube 3 cause the cross-sectional area of the flow path to fluctuate more finely, and the flow
The heat transfer is locally accelerated or decelerated in the concave portion 5 to produce a heat transfer promoting effect.

In addition, the heat transfer surface inside the heat transfer tube 3 has each protrusion 6
A vortex is formed in the wake of the This vortex is caused by the local narrowing of the cross-sectional area of the flow path at the protrusion 6, which accelerates the main stream, lowers the static pressure of the fluid, and creates a pressure difference between the fluid and the part without the protrusion 6. flows from a high-pressure area to a low-pressure area, and these streamlines are combined to create a vertical vortex with a rotation axis in the direction of the tube axis, and the action of this vertical vortex makes it possible to highly promote heat transfer.

Furthermore, if the recesses and protrusion rows on the inner and outer surfaces of the heat exchanger tube 3 are arranged so that adjacent protrusions in the flow direction of the heat exchanger tube are staggered, the heat transfer coefficient is further increased.

Next, other embodiments of the present invention are shown in FIGS. 6 and 7.
This will be explained with reference to the figures.

FIG. 6 is a partial cross-sectional perspective view showing the configuration of a heat exchanger according to another embodiment of the present invention, and FIG. 7 is a partial cross-sectional perspective view showing details of the heat exchanger tube section of FIG.
In the figure, the parts with the same reference numerals as those in FIGS. 1 and 2 are the same parts as in the previous embodiment, so the explanation thereof will be omitted.

In the example shown in FIGS. 6 and 7, fine fins 12 with closely spaced fins are formed on a smooth surface other than the row of recesses 5 provided on the outer surface of the heat transfer tube 3A.

As a result, the same effects as those of the previously described embodiments can be expected, and it is also possible to further improve the heat transfer coefficient due to the Finn effect.

In addition, in the method for processing the heat exchanger tube 3 previously explained with reference to FIG. If the shape is rounded, curvature can be imparted to the shape of the depression formed by this roll.

In this way, if the protrusions formed on the inner surface of the heat transfer tube have a curvature, even if the flow of fluid collides with the protrusions, it will flow along the curvature of the protrusions, and the flow will be caused by the viscous force of the fluid acting on the inner surface of the tube. The effect of the shear stress caused by the heat exchanger tube is reduced, and the effect of erosion caused by the shear stress of the fluid is reduced, which has the effect of improving the corrosion resistance of the heat exchanger tube.

〔Effect of the invention〕

As described above, according to the present invention, the outer surface of the heat transfer tube wrapped around the outer periphery of the inner tube of the double tube is provided with intermittent recesses along a spiral curve, thereby increasing the heat transfer area outside the tube. In addition, it adds turbulence to the fluid flowing outside the heat transfer tube to promote heat transfer, and it also creates turbulence in the fluid by providing continuous circular or elliptical protrusions with curvature on the sides of the protrusions on the inside of the tube. It is possible to provide a heat exchanger and a method for manufacturing the same that make it possible to induce high heat transfer performance.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional perspective view showing the structure of a heat exchanger according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional perspective view showing details of the heat exchanger tube portion of FIG. 1, and FIG. , b, c are front views showing the shape of the protrusions formed on the inner surface of the heat exchanger tube shown in FIG. 2, and FIG. 4 a,
b and c are A- in Fig. 3 a, b, and c, respectively.
A′ arrow view, B-B′ arrow view, C-C′ arrow cross-sectional view, 5th
6 is an explanatory view showing a method of processing a heat exchanger tube according to an embodiment of the present invention, FIG. 6 is a partial cross-sectional perspective view showing the structure of a heat exchanger according to another embodiment of the present invention, and FIG.
The figure is a partial cross-sectional perspective view showing details of the heat exchanger tube section of FIG. 6. 2... Inner tube of double tube, 3, 3A... Heat exchanger tube, 4
...Spiral curve, 5...Concave, 6...Protrusion, 10...Roll, 11...Protrusion, 12...Fine fin.

Claims (1)

[Scope of Claims] 1. In a heat exchanger in which a separate heat transfer tube is wound spirally around the outer circumference of the inner tube of the double tube, the heat transfer tube is wound around the outer circumference of the inner tube of the double tube. A row of depressions is provided intermittently on the outer surface of the heat transfer tube along at least one spiral curve formed on the outer surface of the tube, and as the depressions are formed, the inner surface of the tube has a bottom surface and an arbitrary height. A heat exchanger patented in that the heat exchanger tube has a circular, elliptical, or asymmetrical elliptical cross-sectional shape in its cross-sectional shape, and is provided with a row of protrusions whose cross-sectional area decreases in the height direction. 2. In what is stated in claim 1,
A heat exchanger tube that is wrapped around the outer circumference of the inner tube of a double tube is a heat exchanger tube in which fine fins with closely spaced fins are formed on a smooth surface other than the row of recesses provided on the outer surface of the heat exchanger tube. heat exchanger. 3 In what is stated in claim 1,
The heat exchanger tube that is wrapped around the outer circumference of the inner tube of the double tube is a heat exchanger tube in which the recesses on the outer surface of the heat exchanger tube and the rows of protrusions on the inner surface of the tube are arranged in a staggered manner in the tube axis direction. Heat exchanger. 4. A method for manufacturing a heat exchanger in which a separate heat exchanger tube is wound spirally around the outer circumference of the inner tube of the double tube, in which the heat exchanger tube to be wound around the outer circumference of the inner tube of the double tube, In advance, a gear-shaped roll having an arcuate or rectangular protrusion at the tip is pressed against the outer surface of the heat exchanger tube and rolled along at least one spiral curve, thereby forming the heat exchanger tube. forming intermittent rows of depressions on the outer surface of the tube,
Along with the formation of the depression, a row of protrusions are formed on the inner surface of the tube, the cross-sectional shape of which is circular, elliptical, or asymmetrical elliptic curve at the bottom and at any height, and whose cross-sectional area decreases in the height direction. A method for manufacturing a heat exchanger, which comprises processing the heat exchanger tube as described above, and then wrapping the processed heat transfer tube around the outer periphery of the inner tube of the double tube in a spiral manner. 5. In the method described in claim 4,
A method of manufacturing a heat exchanger in which the arcuate or rectangular protrusions of a gear-shaped roll are rounded to give a curvature to the shape of the recess formed by the roll.