JPS602476Y2 - heat exchanger tube - Google Patents

Description

[Detailed explanation of the invention] The invention consists of 1. This invention mainly relates to improvements in heat transfer tubes employed in double-tube heat exchangers and the like used as condensers.

Conventional heat exchanger tubes of this kind are constructed by winding copper strips or copper wires bent into corrugated shapes around the outer periphery of the original tube.The original tubes include bare tubes, corrugated tubes, inner fin tubes, and A tube with protrusions is used.

However, when the copper strip or copper wire used as the fin is bent into a corrugated shape, there is a limit to the fin pitch if the fin height is limited to a certain height, and the fins can be made finely or <
Cannot be molded.

That is, there is a limit to the heat transfer area ratio between the inside and outside of the tube, making it difficult to improve the heat transfer coefficient on the refrigerant side.

Another drawback is that when winding a corrugated copper strip or copper wire around the original pipe, the corrugation is extended and the fin pitch becomes large because the copper strip or copper wire is stretched.

Furthermore, when using bare pipes, the water side resistance is small but the water side heat transfer coefficient is insufficient, and when using corrugated pipes, the water side resistance is high but the water side heat transfer coefficient is insufficient. There is a drawback that the improvement in the side heat transfer coefficient is small, and when an inner fin tube or a tube with internal projections is used, the processing cost of the original tube increases.

In view of the above-mentioned problems, the present invention has been developed as a so-called double-fluid tube, which is a so-called double-fluid tube in which four strips and convex strips are continuously formed on both the inner and outer surfaces of the tube, which extend in the longitudinal direction parallel to or slightly obliquely to the tube axis. The heat exchanger tube is constructed by wrapping a wire rod made of a thermally conductive metal such as copper wire with a large number of cut and raised pieces with sharp tips integrally formed on the outer surface of the original tube. It is an object of the present invention to provide a heat exchanger tube that can improve the heat transfer coefficients on the water side and the refrigerant side while reducing the resistance on the water side, and is easy to manufacture at low cost.

Hereinafter, a heat exchanger tube according to an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, this heat exchanger tube includes a master tube 1 and a master tube 1
This is composed of a wire rod 2 wound spirally around the outer circumference of the double tube heat exchanger, and this is used as the inner tube of a double tube heat exchanger.
Act as a condenser.

The original tube 1 is a so-called double fluted tube in which grooves 11 and protrusions 12 extending in the longitudinal direction parallel to the tube axis are continuously formed by drawing on both the inner and outer surfaces of the tube.

On the other hand, the wire rod 2 is made of a metal with good thermal conductivity, such as a copper wire, and the wire diameter is 0.5 to 2.0 in the order of φ. Cutting blade 3 as shown
The cut and raised piece with a sharp tip 21゜21... is 0.5~5
They are integrally formed at intervals of TIrIIt.

This wire rod 2 is wound spirally around the outer periphery of the raw tube 1 so that the cut and raised pieces 21, 21,... It is to be soldered to.

In this heat exchanger tube, since a double fluted tube is adopted as the base tube 1, when forming the fins, it is sufficient to simply wind the wire rod 2 without bending the wire rod into a wave shape. The fin height can be freely selected by changing the wire diameter.

Furthermore, the fin pitch can be changed as appropriate by changing the winding pitch.

Furthermore, by employing a double-fluided pipe as the original pipe 1, the resistance on the water side is reduced, so that the heat transfer coefficient on the water side at the same loss wood head can be increased compared to that of a corrugated pipe.

This is also clear from Table 1 and the graphs in FIGS. 4 and 5, which show the experimental results.

Note that lines A and B in FIGS. 4 and 5 indicate the Ray nozzle number R when a corrugated tube and a double fluted tube, which is an embodiment of the present invention, are respectively used as the original tube 1.
It is a graph showing changes in water side heat transfer coefficient Nu/Pr')·4 and friction coefficient f with respect to e.

According to this, the water side heat transfer coefficient is approximately Re0.8 for both the corrugated pipe and the double-fluided pipe of this example.
However, in the case of a corrugated pipe, the coefficient of friction tends to be constant regardless of Re, and in the case of the double fluted pipe of this example, it becomes almost parallel to the Blasius equation as Re increases. It can be seen that the amount decreases to .

Therefore, it can be said that the double fluted pipe of this embodiment is more advantageous than the corrugated pipe in the region where Re is large.

This is thought to be due to the fact that in the double fluted pipe, a flow field similar to that in a smooth pipe is formed along the grooves 11 near the wall surface.

In addition, in the cut and raised pieces 21 with sharp tips formed on the outer surface of the wire 2, the liquid film of the condensed refrigerant becomes very thin at the cut and raised pieces 21, reducing the thermal resistance as much as possible, thereby improving heat transfer. Performance is significantly improved.

Furthermore, in the above embodiment, as shown in FIG. 3, the original tube 1 may be a double fluted tube in which the concave lines 11 and the convex lines 12 are formed slightly obliquely with respect to the tube axis.

Next, the effects of the heat exchanger tube of the present invention will be listed below.

That is, according to the present invention, (1) A double tube formed by continuously forming concave lines 11 and convex lines 12 on both the inner and outer surfaces of the original tube 1, which extend in the longitudinal direction parallel to or slightly obliquely to the tube axis. Since a fluted pipe is used, the resistance on the water side is small despite the large heat transfer area, and the water side heat transfer coefficient at the same head loss can be significantly improved compared to conventional corrugated pipes, etc. (2
) [The pipe 1 is a double-fluided pipe, and the wire rod 2 is made of a thermally conductive metal such as a copper wire, on the outer periphery of which a large number of cut pieces 21, 21, etc. with sharp tips are integrally formed. Since the heat transfer tube is constructed by winding the tube in a spiral, the heat transfer area on the outside of the tube increases, and when acting as a condenser, the refrigerant condensed liquid film on the cut and raised pieces 21, 21, etc. (3) Since the wire rod 2 is simply wrapped around the outer circumference of the base tube 1, which is a double-fluted tube, There are practical effects such as easy manufacturing and low cost, and the ability to freely select the fin pitch and fin height by changing the wire diameter of the wire rod 2.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a heat exchanger tube according to an embodiment of the present invention;
The figure is a cross-sectional view showing a method of processing the wire rod in the heat exchanger tube of FIG. It is a graph showing a comparison of changes in the water side heat transfer coefficient and friction coefficient with respect to the Reynolds number when a conventional corrugated pipe and a double-fluided pipe according to an embodiment of the present invention are respectively used as original pipes. 1... Master tube, 2... Wire rod, 11...
... Concave strip, 12... Convex strip, 21...
section.

Claims (1)

[Scope of utility model registration request] A large number of cut and raised pieces 21 with sharp tips are placed on the outer periphery of the raw tube 1, which has concave shapes 11 and convex shapes 12 that extend in the longitudinal direction parallel to or slightly obliquely with respect to the tube axis and are continuously formed on both the inner and outer surfaces. 21
A wire rod 2 made of a thermally conductive metal such as a copper wire integrally formed on the outer surface is wound spirally so that the cut and raised pieces 21, 21... face outward. A heat exchanger tube characterized by: