JPS6027909B2 - condensing heat transfer tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the performance of vertical condensing heat exchanger tubes by efficiently thinning the condensate film and quickly removing the condensate.

In recent years, ocean thermal power generation, thermal power plants and nuclear power plants
The development of closed Rankine cycle power generation technologies such as low heat drop power generation using E heat, geothermal hot water power generation, and low heat drop power generation using scarlet heat for various industries is underway.

In such systems, electricity is generated by circulating a low-boiling point medium and repeating evaporation and condensation, but in order to improve efficiency, it is necessary to improve the performance of the condenser and evaporator. In particular, it is necessary to reduce the pump power as the in-house power as much as possible, and considering that there is a limit to improving the heat transfer coefficient on the water side, it is essential to improve the heat transfer coefficient on the working fluid side. It becomes technology. Conventionally, fluted pipes have been considered to improve the performance of condensation heat transfer, and the shape has been optimized. It has the disadvantage that as the liquid accumulates in the vertical direction, it becomes smaller, making it unsuitable as the longest condensing tube. In order to improve this, attempts have been made to attach a drain exclusion plate in the middle. Although this is effective to some extent, the manufacturing process is complicated,
In addition, the condensate that has been removed may be sprinkled onto the pipe again, which is not sufficient. In addition, various shapes of horizontal pipes have been proposed, such as high-fin and low-fin, but because the condensers used in low heat drop power generation are large, the condensate falls from the horizontal pipe, and the condensate falls one after another from the lower stage. The disadvantage is that the overall performance deteriorates as the condensation heat transfer surface accumulates. This invention was made in view of the above points, and is based on a fine primer IJ that promotes condensation.
- fins, drain fins for collecting condensate in certain sections and discharging them all at once, and drain fins for efficiently discharging the condensate collected by the drain fins; A condensing heat exchanger tube having a basic structure consisting of a drain bar is provided.

Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a diagram showing the basic structure of a condensing heat exchanger tube as an embodiment of the present invention.

In FIG. 1a, numeral 1 denotes a primary fin formed in a plurality of spiral shapes on the surface of a heat transfer tube made of a material with good thermal conductivity, and has the function of promoting condensation of working fluid vapor. This primary fin 1 is shown in FIG.
It is formed into various uneven shapes as shown in the mouth, c, and here. In the primary fin 1, by optimizing the shape of the fin, it is possible to use the surface tension effect to perform condensation with a thin condensate film, and it is possible to improve the performance of heat transfer more than increasing the surface area. . 2 is a drain fin formed in a spiral shape similar to the primary fin, and has the function of collecting condensate condensed on the surface of the primary fin as described later. 2. A recess 5 is formed on the top surface.

Reference numeral 3 denotes a drain gutter that collects condensate and flows it downward, and is formed in the shape of a groove with a width dd in the vertical direction, as shown in FIG. 1d.

A part of the condensed liquid overcomes each primary fin 1,
The rest flows toward the drain gutter 3 along the valley.
The condensate that has passed over the primary fin flows through a recess 5 formed in the upper part of the drain fin 2 and is collected.
All of the condensed liquid between one pitch Pd (one section) of the drain fin 2 flows into the drain gutter 3. Reference numeral 4 denotes a drain bar attached to one side of the drain gutter 9-3, and this drain bar 4 reliably removes condensed liquid within one section Pd of the drain fin 2, and prevents condensed liquid from entering other sections Pd. Furthermore, it has a role of helping to effectively remove the condensate flowing down inside the drain gutter 3.

That is, by appropriately selecting the width db and shape of the drain bar 4, the condensate can be efficiently drawn into the drain gutter 3, and the width dd of the drain gutter 3 can be made as small as possible so as not to reduce the effective area of the condensing heat exchanger tube. It also serves to cause the condensate to flow down along the drain bar 4, and to quickly separate the condensate from the heat transfer tube. As the drain bar 4, a metal plate, a porous plate, a thin plate made of a polymeric material, etc. can be used.
In consideration of the working fluid vapor flow, the drain bar 4 may have a shape that is narrow at the upper end and widened toward the lower end, for example. 6 is a cold water passage formed inside the heat exchanger tube.

Working fluid vapor enters as indicated by arrow 7 in Figure 1a. 8 shows the entire condensing heat exchanger tube.

Next, an experimental example of the condensing heat exchanger tube 8 having the basic structure as described above and its results will be explained.

FIG. 2 is a conceptual diagram of the experimental apparatus for the condensing heat exchanger tube 8.
In the figure, 9 is an outer cylinder shaped to enclose the condensing heat transfer tube 8, 9' is an inner cylinder for rectifying the flow of steam, 1 is an expansion valve, 11 is a liquid storage tank, and 12 is a working fluid pump. be.
13 is a cold water flow rate adjustment valve, 14 is a thermometer side device, 15 is a pressure gauge side device, 16 is a flow meter, 17 is a water cooler, and 18 is an evaporator.

The working fluid vapor flows into the outer cylinder 9 through the expansion valve 10;
After the flow of steam is rectified by the inner cylinder 9', it is condensed into a heat transfer tube 8.
The condensed liquid is collected in a sump tank 11 and sent to the evaporator 18 again by the working fluid pump 12. On the other hand, the cooling water flows into the cold water passage 6 of the condensing heat exchanger tube 8 from the water cooler 17, obtains heat from the inner surface of the cold water passage 6 of the condensing heat exchanger tube 8, passes through the cold water flow rate adjustment valve 13, and returns to the water cooler 17. sent to. FIG. 3 is a diagram showing an example of the shape of the condensing heat exchanger tube 8 used in the experiment.

In the figure, A is a portion where a spiral double fin consisting of the primary fin 1 and drain fin 2 is formed, and B is a smooth portion at both ends. Details of part A are shown in FIGS. 4a to 4d. That is, FIG. 4a shows part of the primary fin 1 and drain fin 2, and enlarged views of each fin are shown in FIGS. 4c and 4d. Figure 4b is the fourth
Figure a is a side view of figure a; Also, ai is the outer diameter of the primary fin 1, hp is the height, pp is the pitch width,
hd indicates the height of the drain fin 2. a. is the outer diameter of the drain fin 2. To give an example of the dimensions, the length of part A is 990 ribs, the length of part B is 55 willow, and the inner diameter of cooling channel 6 is 16 side, a.

Is it on the 24th side? , the number of threads on drain fin 2 is 4 per inch,
AI is 21.6 ribs, HP is 0.8 ribs, Pp is 1. Q proboscis,
HD is 2.0 ships, DD is 2 pigs. In the experimental apparatus shown in FIG. 2 described above, using the condensing heat transfer tube 8 shown in FIG.
Heat transfer performance experiments were conducted over a range of approximately 000 to 15,000 kcal/h. Performance was evaluated based on the actual area on the working fluid side. FIG. 5 is a diagram showing the relationship between the condensation heat transfer coefficient Qc and the heat flux q. Heat tube 8 (marked with square) and smooth tube (marked with ●)
We have shown the experimental values for easy comparison between the two. In FIG. 4, the experimental value for the smooth tube is about 30% higher than the value based on Nutselt's film condensation theory, and this is thought to be due to the effect of vapor flow. When comparing the performance of the smooth tube and the condensing heat transfer tube 8 according to the present invention based on the actual area on the working fluid side, it was found that the performance is 4 to 6 times higher. When the water flow rate is set to 2/s to obtain the same processing heat amount and the same condensation temperature, approximately 1/2 of that of a smooth pipe.
It was experimentally confirmed by reducing the number that 5 is sufficient. Although the spiral double fin type condensing heat exchanger tube 8 according to the present invention used in the above experiment has a short effective tube length of 900 legs, it is fully predicted from its structure that it will be more effective if it is made longer.

That is, it can be said that this spiral double fin type condensing heat exchanger tube 8 is suitable for increasing the length. In the above experimental example, the shape parameters of the condensing heat exchanger tube 8 have not yet been optimized, but as shown in FIG. 1, the pitch Pd of the drain fin 2, the height hd of the drain fin 2, height hp, pitch Pp of primary fissure 1, number of circumferential direction of drain gutter 3, and width dd
, the width db of the drain bar 4, and their shape can be changed to select optimal shape parameters that suit the operating conditions such as each working fluid, temperature, heat flow direction, etc. FIG. 6 is a diagram showing an example of a modularized long condensing heat exchanger tube east, and FIG. 7 is a partially enlarged view thereof. In the same figure, 19
1 is the condensing heat exchanger tube east, which consists of a plurality of condensing heat exchanger tubes 8 having the basic structure shown in FIG. The intermediate drain fin flange 21 is the drain guide of the condensing heat exchanger tube east 19.

The condensate collected with the primary fin I, drain fin 2 and drain gutter 3 flows down through the drain guide 21 via the intermediate drain fin flange 20. 8th
The figure is a plan cross-sectional view of the condenser.
9 are housed in the inner cylinder 9' to form a condenser.

Since the spiral double fin type condensing heat transfer tube 8 as shown in FIG. 1 as an embodiment of the invention described above can achieve high performance condensing heat transfer, the number of condensing heat transfer tubes 8 can be reduced.

For example, although it depends on the heat transfer coefficient on the cooling side, the above experimental results show that when seawater is used, the number of heat exchanger tubes can be reduced to about 2.5 times that of smooth heat exchanger tubes. Predictable. Therefore, it can be expected to have a great effect on cost and compactness. Particularly in low temperature difference power generation systems such as ocean temperature difference power generation, the size of the heat exchanger is large, so using the spiral double fin type condensing heat transfer tube 8 of this invention, which requires fewer pieces, can make it more compact. This makes it possible to greatly contribute to reducing the overall system cost by reducing piping and containment vessel dimensions (for example, offshore structures). Further, the condensing heat exchanger tube 8 shown as an embodiment of the present invention has succeeded in removing restrictions on length to some extent, and it becomes possible to provide a large degree of freedom in determining the structural layout of the entire system. As explained in detail above, the condensing heat exchanger tube according to the present invention has a drain fin formed in a spiral shape for collecting and discharging the condensed liquid by dividing it into sections. It has a drain gutter integrated with a drain bar that further collectively removes the condensed liquid in the vertical direction of the pipe, and is formed in a spiral shape to promote condensation heat transfer in the section between the drain fin and the next drain fin. The basic structure is a spiral double fin type condensing heat transfer tube with condensation promoting fins, which provides high-performance condensing heat transfer that cannot be achieved with conventional condensing heat transfer tubes, making it extremely useful for making heat exchangers more compact. Demonstrates excellent effects.

Moreover, by making the condensing tube into a module structure, the condensing heat exchanger tube can be made of a good size, which has an extremely excellent effect of providing a large degree of freedom in determining the structural layout of the entire system.

[Brief explanation of the drawing]

Figures 1a to 1d are diagrams showing the basic structure of the condensing heat exchanger tube according to the present invention, and Figure 1a is a partially cutaway view of the condensing heat exchanger tube;
Figure b is a diagram showing an example of the shape of the primary fin, Figure 1 c
Figure 1d shows an example of the shape of a drain fin, Figure 1d is a cross-sectional view of a condensing heat transfer tube, Figure 2 is a system diagram of the experimental equipment, and Figure 3 shows the shape of the condensing heat transfer tube used in the experiment. Figures, Figures 4a-d
is an enlarged view of the main part of Fig. 3, Fig. 4 a is a partial side view, Fig. 4 b is a front view, Fig. 4 c and d are primary fins,
A cross-sectional view of the drain fin, Figure 5 is a diagram showing the experimental results, Figure 6 is a diagram showing an example of a modularized long condensing heat exchanger tube east, and Figure 7 is an enlarged view of the main part of Figure 6. , FIG. 8 is a plan cross-sectional view of the condenser. In the diagram, 1 is the primary fin, 2 is the drain fin, and 3 is the primary fin.
4 is a drain gutter, 4 is a drain bar, 5 is a concave portion on the upper surface of the drain fin, 6 is a cold water passage, 8 is a condensing heat exchanger tube, 19 is a condensing heat exchanger tube east, 20 is an intermediate drain fin flange, and 21 is a drain guide. Figure 1 Figure 7 Figure 2 Figure 4 Shipboard Figure 5 Figure 6 Figure 8

Claims (1)

[Claims] 1 It has a drain fin formed in a spiral shape to collect and remove the condensed liquid in sections, and is integrated with a drain bar that further collects and removes the collected condensed liquid in the vertical direction of the pipe. What is claimed is: 1. A condensing heat exchanger tube having a drain gutter, and a primary fin formed in a spiral shape for promoting cohesive heat transfer in a section between the drain fin and the next drain fin.