JPS5841437B2 - heat exchanger tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in heat exchanger tubes used in various heat exchangers, such as condensers and condensers.

In general, power plants that generate power to circulate working fluids such as steam, chemical plants that refine substances,
BACKGROUND ART In factories and the like where materials are recovered, condensers are used to convert vapor into liquid.

Conventionally, the heat transfer tubes of condensers used in this type of plant have either a smooth surface or a finned tube with fins on the outer surface of the tube vertically or spirally along the length of the tube. Many were used in tube groups.

However, when steam condenses on the surface of these tubes, the condensation heat transfer coefficient is not very large, and therefore a large number of heat transfer surfaces are required to obtain the desired amount of condensation.

As a result, it has the disadvantage that manufacturing costs are high even though very high transmission performance cannot be obtained.

In order to eliminate these drawbacks, various proposals have been made and various developments have been made in recent years.

For example, a fluidized pipe has been developed in which a large number of vertical stripes are provided on the inner and outer surfaces of the heat exchanger tube, or only on one side thereof, in parallel along the length of the heat exchanger tube.

This type of heat exchanger tube has better performance than conventional smooth surface heat exchanger tubes or finned heat exchanger tubes when the amount of condensation is small.

However, when the amount of condensation increases, the condensate becomes a film, so
Especially in the lower part of the heat exchanger tube, the film becomes thicker.
This has the drawback that the purpose of providing the vertical stripes on the surface of the heat exchanger tube is diminished, and the condensation performance is significantly reduced.

Therefore, when a fluidized tube is used in a condenser with a large amount of condensation, various measures are required in the same way as with conventional smooth tubes and fin spacing.

For this reason, there is a drawback that manufacturing requires a large number of man-hours.

In addition, recently, a heat exchanger tube called a corrugated tube has been developed, which has grooves inclined in the right-hand thread direction on its surface.

This corrugated pipe is somewhat efficient when used horizontally, but when the corrugated pipe is used vertically, the efficiency is not much different from that of conventional smooth pipes, and the performance decreases. There are drawbacks.

Therefore, as shown in the specification and drawings of Japanese Patent Application No. 53-161081, the present inventor has developed a heat transfer tube that is extremely efficient even when vertically arranged.

That is, an inclined groove inclined in the direction of the left-hand thread was formed on the outer surface of the heat exchanger tube.

It is an object of the present invention to further improve such a heat exchanger tube and to provide a heat exchanger tube in which condensate can be easily scattered from the surface of the heat exchanger tube.

The gist of this invention is to provide two spirally inclined grooves in the direction of left-hand threads that are provided in close proximity to each other, and a groove that is located between the two spirally inclined grooves, and whose top portion is on the same level as the heat transfer surface. or a helical protrusion set to less than that, and one of the spiral inclined grooves.
This is a vertical condensing heat transfer tube consisting of a wide smooth straight pipe section provided within two pitches, and the lower surface of the spiral protrusion constitutes a flank for the condensate.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

First, the heat exchanger tube according to the present invention shown in FIG. 1 will be explained.

The outer surface of the heat exchanger tube 1 features a long and narrow inclined groove 2 inclined in the direction of the left-hand thread.

Although the details of the inclined groove 2 are not shown in FIG. 1 for the sake of simplification, an example thereof is shown in FIG. 2, which will be described later.

In the embodiment of FIG. 1, the inclined grooves 2 are formed continuously over a number of pitches.

For the purposes of this specification, the pitch P is I, which the groove advances through one rotation.
shall mean J-do.

Although the heat transfer surface 1a should have a considerable width, the spacing between the inclined grooves 2 may be varied depending on the position of the heat transfer tube 1 as required.

For example, when the heat exchanger tubes 1 are arranged vertically, the interval at the lower part thereof can be made longer.

In addition, since the inclined groove 2 is formed in the left-hand thread direction at a predetermined inclination angle A, when the heat exchanger tube 1 is arranged vertically, the inclined groove 2 is directed downward to the right when viewed from any viewpoint of 3600. It is sloping.

Taking a circular tube as an example, when the outer diameter of the heat exchanger tube 1 is D, it is preferable that the pitch P is 2D to 3D.

Good results are obtained when the depth of the inclined groove 2 is approximately 1.5 to 4 mm.

FIG. 2 shows an example of the cross section of the inclined groove 2 shown in FIG.

The shape of the inclined grooves 2 is such that the condensate is easily drawn into the inclined grooves 2 from the heat transfer surface 1a, so that the space between the heat transfer surface and the inclined grooves, that is, the upper edge of the inclined grooves is shaped without corners. It is desirable to allow the liquid to flow easily.

In the embodiment of FIG. 2, the first groove 2a of the heat exchanger tube 1
and a second groove 2c are formed, and as a result of forming these grooves 2a and 20, a spiral protrusion is created between these grooves.

Therefore, the first groove 2a is formed by being continuously recessed from the surface 1a of the heat exchanger tube 10, then the helical protrusion 2b continues, and the second groove 2c is again along the first groove 2aK.
is formed and connected to the surface 1a of the heat exchanger tube 1.

That is, the first and second grooves 2a. 2c becomes a double groove,
An arcuate helical protrusion 2b exists between them.

The top of this helical protrusion 2b is located at the same level as or below the heat transfer surface 1a.

Note that the helical protrusion 2b is not limited to a smooth curved surface as shown in the figure, but may preferably have another shape (for example, an acute angle shape).

The function of the heat exchanger tube described above will be explained.

Generally speaking, when vapor condenses on a smooth outer peripheral surface of a vertically arranged circular tube, the thickness of the condensate gradually increases from the top to the bottom.

The condensation heat transfer coefficient decreases as it goes down the heat exchanger tube.

When the amount of condensation increases, the condensed liquid formed on the outer circumferential surface of the heat transfer tube is affected by the Coriolis force caused by the rotation of the earth, and flows down the outer circumferential surface of the heat transfer tube while rotating in the direction of a left-hand thread. It has the property of

Since the condensate formed on the surface of the heat transfer tube has such characteristics, if vertical stripes or right-handed inclined grooves are formed on the surface of the heat transfer tube, as in conventional heat transfer tubes, condensation will be prevented. The liquid does not flow down smoothly, and as a result, the condensed liquid often flows in clumps on the heat transfer surface, deteriorating the heat transfer coefficient of condensation.

On the other hand, if an inclined groove is formed on the surface 1a of the heat exchanger tube 1 in the direction of the left-hand screw, as in the present invention, it matches the flow characteristics of the liquid condensed on the surface 1a of the heat exchanger tube 1, and the condensed liquid will flow down smoothly.

That is, the liquid condensed on the surface 1a of the heat exchanger tube 10 first flows into the inclined groove 24? It flows into the first groove 2a, and then smoothly flows down the groove 2a (/ca).

The flow of such condensate becomes faster as it goes downward, and finally it scatters from the groove 2a.

At this time, the spiral protrusions have the effect of causing the condensate to jump out.

Furthermore, the lower surface 2d of the spiral convex strip acts as a relief surface to shake off the flying condensate, so that the condensate does not remain in the groove forever and is effectively scattered.

Therefore, the thickness of the condensed film is suppressed to a certain value or less over the entire length of the heat exchanger tube 1.

Furthermore, since the condensate is pulled from the surface 1a of the heat exchanger tube 10 toward the inclined groove 2 by the surface tension of the condensate, condensation on the surface 1aK is further promoted.

Therefore, a phenomenon similar to droplet condensation occurs on the surface 1aK of the heat exchanger tube 1, instead of film condensation as in the conventional case.

For this reason, the condensation heat transfer coefficient of the heat exchanger tube 1 shown in FIGS. 1 and 2 is significantly higher than that of the conventional smooth circular heat exchanger tube.

Although not shown in the figure, vertical stripes can be formed along the length direction of the heat exchanger tube 1.

FIG. 3 shows another embodiment of the heat exchanger tube according to the present invention.

In this example, a smooth outer surface portion 3 is provided over a predetermined width W where no inclined groove 2 is present.

Except for the smooth outer surface portion 3 provided along this width W, the shape is virtually the same as that of the embodiment shown in FIGS. Omitted.

For example, in a vertical condenser, these smooth outer surface portions 3 are provided in the middle of a large number of heat exchanger tubes arranged vertically in parallel inside, and partitions are placed there. It can be used when placing boards.

FIGS. 4 and 5 show still other embodiments of the heat exchanger tube according to the present invention.

FIG. 5 shows the heat exchanger tube shown in FIG. 4 rotated by about 90 degrees around the axis of the heat exchanger tube.

In this embodiment, the inclined grooves 4 and 5 inclined in the direction of the left-hand thread are formed independently and intermittently at every half pitch, and the intermittent inclined grooves 4 and 5 are formed along the length of the heat exchanger tube 1. They are connected by two long vertical grooves 6 and 7 along the direction.

By providing the vertical grooves 6 and 7 in this way, the condensate that has swirled and flowed from the inclined grooves 4 and 5 is collected in these vertical grooves 6 and 7 and flows downward.

Therefore, the condensate can be flowed down below the heat transfer tube very effectively.

The combination of the inclined grooves 4 and 5 with the two longitudinal grooves 6 and 7 further improves the condensation performance on the surface 1a of the heat exchanger tube 10.

Note that also in the embodiments shown in FIGS. 4 and 5,
As shown in FIG. 3, it is possible to provide a smooth surface portion in which neither the inclined grooves 4 and 5 nor the longitudinal grooves 6 and 7 are present at a predetermined location.

Although not shown in the figure, the length of the heat exchanger tube 1 is formed on the outer surface of the heat exchanger tube 1 (excluding the portion 3 having the width W) between the above-mentioned surface 1a, that is, between the inclined grooves 2 and 4.5. Forming a large number of vertical stripes along the direction further improves the heat transfer effect.

The angle of inclination of the inclined groove 2°4.5 formed on the outer surface of the heat exchanger tube 1 differs depending on the type of condensate, but the optimum inclination is determined for each by taking into account the flowing properties of the sulfuric liquid. Setting the angle smoothes the flow down, increases the flow velocity, and blows away the condensate, resulting in heat transfer that approximates vortex condensation.

In any of the embodiments shown in the figures, if a spiral protrusion is formed adjacent to the groove as shown in Fig. 2, the condensation effect can be increased.

Since the heat exchanger tube according to the present invention is constructed as described above, a thick film of condensate is unlikely to form over the entire heat exchanger tube, and even if it does occur, it is maintained very thin overall.

Therefore, the heat exchanger tube according to the present invention can obtain a significantly higher heat transfer effect than a conventional heat exchanger tube with a smooth surface or a heat exchanger tube with an inclined groove formed in the right-hand thread direction.

The invention is not limited to the embodiments described above.

The heat exchanger tube of the present invention is particularly effective when used in a condenser, but it also provides sufficient effects when used in other heat exchangers.

The heat exchanger tube of the present invention is particularly effective when used in a vertical multi-tube condenser or heat exchanger.

Heat exchanger tubes include not only circular tubes but also elliptical tubes and others.

In the case of an elliptical tube, it is desirable to form the vertical grooves on the outer surface in the direction of the minor axis.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing an example of a heat exchanger tube according to the present invention;
FIG. 2 is a sectional view showing an example of the inclined groove of the heat exchanger tube shown in FIG. 1, FIG. 3 is a front view showing another example of the heat exchanger tube according to the present invention, and FIG. 4 is a heat exchanger tube according to the present invention. FIG. 5 is a schematic front view showing still another example of the heat exchanger tube shown in FIG. 4 rotated about 90 degrees around its axis. DESCRIPTION OF SYMBOLS 1... Heat exchanger tube, 2... Inclined groove, 2a... First groove, 2b... Helical convex strip, 2c... Second groove, 3...
... Smooth surface portion of heat exchanger tube 1, 4, 5... inclined groove, 6°7... vertical groove.

Claims (1)

[Claims] 1. Two spiral inclined grooves in the direction of left-hand threads provided in close proximity, and a spiral located between the two spiral inclined grooves, the top of which is set at the same level or lower than the heat transfer surface. A vertical type consisting of a shaped protrusion and a wide smooth straight pipe section provided within one pitch of the spiral inclined groove, the lower surface of the spiral protrusion forming a flank for the condensate. Heat exchanger tube for condensation.