JPS5938595A - Heat transfer tube for condensation heat - Google Patents

Abstract

PURPOSE:To obtain a heat transfer tube of which heat transferring ability for condensation heat is high, by constituting the heat transfer tube of drain fins which gather to discharge condensed liquid every specified section, a drain gutter into which the condensed liquid collected by the drain fins are all gathered, and a drain bar which serves to drain the gathered liquid efficiently. CONSTITUTION:A drain fin 2 has a function to collect liquid condensed on the surface of a primary fine 1, and a recess part 5 is formed on the upper surface of it. A drain gutter 3 is formed vertically on the surface of a tube like a channel with the width dd. The condensed liquid crossing over the primary fin 1 is gathered, passing through the recess part 5 formed on the upper surface of the drain fin 2. All condensed liquid in a pitch Pd (one section) of a drain fin 2 are led into the drain gutter 3. The drain bar 4 serves to prevent the condensed liquid from penetrating into other sections Pd, as well as to certainly discharge the condensed liquid from one section Pd of the drain fin 2, and also serves to help the condensed liquid to be discharged effectively, flowing down through the drain gutter 3.

Description

[Detailed Description of the Invention] This invention relates to improving the performance of vertical condensing heat transfer tubes by efficiently thinning the condensate film and quickly removing the condensate.In recent years, ocean temperature differences have been increasing. Power generation, low heat drop power generation using waste heat from thermal power plants and nuclear power plants, power generation using geothermal hot water.

The development of closed Rankine cycle power generation technology, such as low heat drop power generation using waste heat from various industries, is underway. In such a system, 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, to improve the performance of condensing heat transfer, a vertically grooved (full-tended) tube has been considered, and although optimization of the shape is effective to some extent, the manufacturing process is complicated, and the condensate It is not enough that the water is sprinkled back into the pipe. In addition, various shapes of horizontal pipes have been proposed, such as high-fin and low-fin, but because the condensers used in low thermal drop power generation are large, the condensate falls from the horizontal pipe, and condensation occurs one after another in the lower stage. Since it accumulates on the heat transfer surface, it has the disadvantage that the overall performance deteriorates.

This invention was made in consideration of the above points, and includes a fine primary fin that promotes condensation, a drain fin that collects condensate in a certain section and removes it all at once, and the drain fin. The present invention provides a condensing heat exchanger tube having a basic structure consisting of a drain gutter for further collectively discharging the condensate collected in the condensate and a drain bar for efficiently draining. 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. 1(a), 1 is a heat exchanger tube surface 1 made of a material with good thermal conductivity! I? , % spirally formed primary fins that promote condensation of working fluid vapor. This primary fin 1 is shown in (a), (b), and (c) in Fig. 1(b).
As shown in , (d), it is formed in various uneven shapes.

In the primary fin 1, by optimizing the shape of the fin, it is possible to achieve condensation with a thin condensate film using the surface tension effect, and to improve the performance of heat transfer more than increasing the surface area. can. 2 is a drain fin formed in a spiral shape similar to the primary fin 1, and has the function of collecting condensate condensed on the surface of the primary fin 10 as described later.
As shown in FIGS. 1 to 5, a recess 5 is formed on the upper surface of the drain fin 2. 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. 1(d). A portion of the condensate is distributed to each primary fin 1
, and the rest flows along the valley towards Drain Gutter 3. The condensate that has passed over the primary fin 1 flows through a recess 5 formed in the upper part of the drain fin 2 and is collected. All of the condensate from one pinch (one section) of the drain fin 2 flows into the drain gutter 3. 4
(above) is a drain bar attached to one side of the brick fin 3, and this drain bar 4 is connected to one section 1 of the drain fin 2.
) While ensuring that condensate is removed within d, other sections T
) It has the role of preventing the condensate from entering d and assisting in the effective removal of the condensate flowing down inside the pressure 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 large as possible (
The function is to make the condensate small so as not to reduce the effective area of the condensing heat transfer tube, and to cause the condensate to flow down along the drain bar 4 to draw the condensate away more quickly than the heat transfer tube. Drain bar 4 has a metal plate and a porous plate.

A thin plate made of polymeric material or the like 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. The working fluid vapor is indicated by arrow 7 in Fig. 1(a).
There is an inflow as shown in . 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 same picture, 9
Reference numeral denotes an outer cylinder having a shape to enclose the condensing heat transfer tube 8, 9' an inner cylinder for rectifying the flow of steam, 10 an expansion valve, 11 a liquid storage tank, and 12 a working fluid pump. 13 is a cold water flow regulating valve, 14 is a temperature side measuring device, 15 is a pressure measuring device, 16 is a flow meter, IT 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 from the water cooler 1T into the cold water passage 6 of the condensing heat exchanger tube 8, 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 the Svairalda pull fin consisting of the primary fin 1 and drain fin 2 is formed, and B is a smooth portion at both ends. The details of the section are shown in FIGS. 4(a) to 4(d). That is,
Figure 4(a) shows primary fin 1 and drain fin 2.
An enlarged view of each fin is shown in Figure 4(c).
, <d). FIG. 4(b) is a side view of FIG. 4(a).

Further, s al indicates the outer diameter of the primary fin 1, hp indicates the height, Pp indicates the pitch width, and hd indicates the height of the drain fin 2. aO is the outer diameter of the drain fin 2.

To give an example of the dimensions, the length of the part B is 990mm, the length of the part B is 55mm, the inner diameter of the cooling water channel 6 &t16mφ,
ao has 24 threads in diameter, and the number of drain fins is 20 threads per inch.
, al is 21.6 rant hp is 0.8 mm.

p2 is lomml hd is 2. Owrm+dr+ becomes the 2nd step.

In the experimental apparatus shown in FIG. 2 described above, using the condensing heat transfer tube 8 shown in FIG.
0℃, heat flux 3000-15000kc a I/7
Heat transfer performance experiments were conducted over a region of about 7” h.

Performance was evaluated based on the actual area on the working fluid side. Figure 5 shows the condensing heat transfer coefficient α. This figure shows the relationship between the heat flux q and the condensing heat exchanger tube 8 (marked 0) having a spiral double fin having the basic structure shown in FIG. 1, which is an embodiment of the present invention. and experimental values for a smooth tube (marked with a *) are shown to facilitate comparison between the two. In Figure 4, the experimental values for the smooth tube are:
The obtained value is approximately 30% higher than the value obtained from Nutsselt's theory of film condensation, but this seems to be due to the effect of vapor flow. Comparing the performance of the smooth tube and the condensing heat exchanger tube 8 according to the present invention based on the actual area on the working fluid side, it is 4 to 6.
I found out that you can get double the value. Water flow rate 2 m/
It was experimentally confirmed by reducing the number of tubes that when K is set to obtain the same amount of processing heat and the same condensation temperature as s, only about 1/25 of a smooth tube is required.

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 fins, 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 addition, 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. - Height hp of the fins 1, pitch pp of the primary fins 1, number and width in the circumferential direction of the drain gutter 3, width dd, width db of the drain bar 4, and their shapes, each working fluid and temperature, Optimal shape parameters can be selected that suit operating conditions such as heat flux.

FIG. 6 is a diagram showing an example of a modularized long condensing heat exchanger tube bundle, and FIG. 7 is a partially enlarged view thereof. Primary fin 1. Drain fin 2 and drain gutter 3
The collected condensate flows down through the drain guide 21 via the intermediate drain fin flange 20.

FIG. 8 is a plan cross-sectional view of the condenser, and since the condensing tube 8 shown in FIG. 6 can achieve high-performance condensing heat transfer, it can be predicted from the condensation results. Therefore, it can be expected to have a great effect on cost and compactness. In particular, in low temperature difference power generation systems such as ocean temperature difference power generation, the size of the heat exchanger becomes large, so if you use the spiral double fin type condensing heat transfer G8 of this invention, which requires fewer heat exchangers, it will be easier to use. It can also greatly contribute to reducing the overall system cost, such as by routing 1-hole piping and reducing the size of the containment vessel (for example, an offshore structure), which enables ε.

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 transfer tube according to the present invention divides the condensed liquid into sections, collects it, and removes it.
The basic structure is a spiral-shaped condensing heat exchanger tube with pressure-formed condensation promoting fins, which provide high performance that cannot be obtained with conventional condensing heat exchanger tubes. The condensation heat transfer is achieved, and the heat exchanger is extremely effective in making the heat exchanger more compact. Further, by making the condensing tubes into a module structure, it is possible to form a bundle of condensing heat transfer tubes that is longer than the button, 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 drawings]

Figures 1(a) to 1(d) show the basic structure of the condensing heat exchanger tube according to the present invention; Figure 1(a) is a partially cutaway view of the condensing heat exchanger tube; Figure 1 b) shows an example of the shape of a primary fin, Figure 1 (c) shows an example of the shape of a drain fin, Figure 1 (d) is a cross-sectional view of a condensing heat exchanger tube, and Figure 2 shows an example of the shape of a drain fin. System diagram of the experimental equipment, Figure 3 is a diagram showing the cedar shape of the condensing heat exchanger tube used in the experiment, Figures 4 (a) to (d) are enlarged views of the main parts of Figure 3, Figure 4 (a) is a partial side view, Fig. 4 (b)
is a front view, FIG. 4(C). (d) is a cross-sectional view of the primary fin and drain fin,
Fig. 5 is a diagram showing the experimental results, Fig. 6 is a module condensing heat exchanger tube, 19 is a condensing heat exchanger tube bundle, 20 is an intermediate drain y) 7 (y7
'y9 ・2191+"1"ga"'Fr7-)Mo1-:1 1,-); ・:

Claims (1)

[Claims] It has a drain fin formed in a spiral shape for collecting and discharging the condensed liquid in sections, and has a drain gutter for discharging the condensed liquid collected there in the vertical direction of the pipe. . A condensing heat exchanger tube comprising a spirally formed primary fin for promoting condensing heat transfer in a section between the drain fin and the next drain fin.