JPH0221103A - Inner radial small lines-inserted vaporization pipe designed to inhibit the generation of droplets - Google Patents

Abstract

PURPOSE:To facilitate the manufacture inside a pipe and inhibit the generation of droplets effectively by inserting small lines in an intersection direction against the direction of flow inside a heat transfer pipe and laying out them in a spiral manner. CONSTITUTION:The cross section of a small line 2 to be inserted into a smooth heat transfer pipe 1 may be specified as circular, rectangular, and triangular. With regards to a cross sectional dimension (d), any size is acceptable whether it is small or large. In terms of its material, an elastic metal or plastic is serviceable. Many combinations can be used in terms of the number of spiral (n) and spiral pitch (p) when inserted in a spiral manner. A small line can be installed locally, say, to a required spot 1 or along the full length of the heat transfer pipe. Droplets 3 generated from a liquid film flow 5 are generated from the tip of the waves produced on the interface, when the liquid film flow are pulled by a high speed steam flow. When the small lines are inserted, the liquid will flow, filling the grooves between the small lines 2, which makes the surface of the liquid film relatively flat and interrupts the formation of waves, thereby inhibiting the generation of droplets.

Description

[Detailed description of the invention] Purpose of the invention Industrial field of application: The present invention relates to an evaporation tube used in a boiler or various steam generators, and mainly relates to a once-through type evaporation tube without a gas-liquid separation section. Used in steam generators.

Conventional technology: Conventional steam generators have the disadvantage that a large amount of liquid droplets get mixed into the air of the evaporator tube, which has a smooth inner surface, and that the liquid in contact with the heat transfer surface (I) quickly disappears, thereby deteriorating the heat transfer performance. In addition, if a large amount of droplets are mixed into the steam, it will cause performance degradation and material corrosion of equipment that uses this wet steam as a working fluid. Therefore, in order to completely evaporate these droplets in the vapor, an excessively large heat transfer area is required.

The problem that invention tries to solve! II: A factor that significantly degrades performance in conventional technology is a phenomenon called billiard. This is because evaporation progresses as the liquid flows through the evaporation tube, and as the proportion of vapor increases and the flow velocity at the center of the tube increases, a large amount of liquid is stripped away from the liquid film flowing on the inner wall of the tube. As a result, the liquid film disappears quickly due to evaporation, causing the wall surface to dry out.

On the other hand, among those developed as evaporation tubes, those structurally similar to the present case 1 are used, for example, in high-temperature pressure wheels where the heat load (heat passage per unit time, area ff1) is high. There is a hollow tube with a spiral groove on the inside.

Si+enson, H, S,, at, al, Tra
ns, ^SHE, Eng, for Power,
84. (1962-10), 365° This evaporation tube is aimed at improving the heat transfer deterioration phenomenon in the case of a relatively high heat load, and its purpose is different from that of the present invention. In addition, there are structural problems such as difficulty in machining the inner surface of the tube and making it economically expensive.

In summary, the problem to be solved by the present invention is to effectively suppress the generation of droplets described above using a method that is relatively easy to manufacture within a pipe.

Means for solving the problems of the invention: The means used in the present invention is to insert thin wires into the inner surface of the heat exchanger tube in a direction crossing the flow direction, especially in a spiral shape. It is to arrange.

Effect: Figure 1 shows the effect of the above means as aj, and shows the process of droplet generation from the liquid film (1-1) and the situation of the liquid film flow when inserting the thin wire (1-2). It shows.

In the figure, (1) indicates a heat exchanger tube, and (2) indicates a thin wire. A droplet (3) is generated from the tip of a wave (6) generated at the interface when a liquid film flow (5) is pulled by a high-speed vapor flow (4) (1-1).

Then, when the previous mm is inserted, the liquid fills the groove between the 10 lines and flows, making the surface of the liquid film relatively flat, making it difficult to form waves, and suppressing the generation of droplets (1 -2).

On the other hand, from a manufacturing point of view, by using elastic materials such as metal or flask for the thin wire, it can be made to adhere closely to the tube wall, so it can be installed relatively easily without machining the inner surface of the tube. can.

Example: FIG. 2 shows an embodiment of the invention.

(a) The cross-section of the thin wire inserted into the smooth inner surface of the evaporation tube may be circular, rectangular, triangular, etc., and the cross-sectional dimension d may also be large or small. (b) As the material, elastic metals, plastics, etc. can be used. (C) In the case of spiral insertion, there are many possible combinations of the values of the helical loss n and the helical fp. In addition, (d) the insertion method may be either locally provided at the required location l or over the entire length.

Effects of the Invention According to the present invention, the surface of the liquid film on the inner surface of the tube can be flattened and the generation of droplets can be suppressed. This makes it possible to reduce the amount of droplets contained in the generated steam and to manufacture a small-sized steam generator.

FIG. 3 shows an example of the effect of suppressing droplet generation, where the vertical axis shows the ratio E (%) of generated droplets to the total liquid amount, and the horizontal axis shows the steam flow rate Ug (m/s). In the figure, the mark indicates an inner diameter of 19.
When inserting 4 thin wires with a diameter of 3.2 mm into a 5 aIll tube in a spiral shape with 9 edges and 500 mm, the ◇ mark indicates 8 thin wires with a rectangular cross section of 2 +++ g x 2.5 mm. , which is the case when the tube is inserted with a zero edge of 1000 l11 m, and it can be seen that the amount of droplets generated is reduced compared to the smooth tube indicated by O, and is about 1/2 at the minimum. Note that the multiple dates indicate the number of experiments.

[Brief explanation of the drawing]

Figure 1 Figure 1-1 for explaining the details of the present invention Figure 1-2 for explaining the droplet generation process 1
Diagram 2 of the mouth tube showing the situation when the 11 wire is inserted Figure 3 Embodiment of the present invention Diagram showing the effect of the present invention Heat transfer tube Thin wire Droplet Vapor flow Liquid film Flow surface wave diagram (d) (C) Figure 2

Claims (2)

[Claims] (1) Evaporation tube with thin wires installed on the inner surface of the tube in a direction that intersects with the flow direction (2) The evaporation tube according to claim 1, wherein the thin wire is arranged in a spiral shape.