JPH02638B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a condensing heat exchanger tube, a heat exchanger for ocean temperature difference power generation, a heat exchanger for low heat drop power generation using waste heat,
It can be used in absorption refrigerators, heat pumps, etc. Conventional technology In recent years, closed Rankine cycle power generation technologies have been developed, such as ocean temperature difference power generation, low heat drop power generation using waste heat from thermal power plants and nuclear power plants, geothermal hot water power generation, and low heat drop power generation using waste heat from various industries. being admired. 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, considering that there is a limit to improving the heat transfer coefficient on the water side because the pump power as internal power needs to be as small as possible, it is essential to improve the heat transfer coefficient on the working fluid side. technology. Conventionally, to improve the performance of condensing heat transfer, a fluted tube as shown in FIG. 6 has been considered, and the shape has been optimized. This full-tipped tube draws the condensate into the troughs a shown in Figure 7, and although the condensate film becomes thinner at the protrusions b, the condensate accumulates in the axial direction, resulting in a large liquid film distribution in the axial direction. The performance deteriorates as the length of the tube increases. 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 is likely to re-sprinkle into the pipe, which is not enough. In addition, various shapes of horizontal pipes have been proposed, such as high-in and low-in, but condensers used in low thermal drop power generation are larger, so condensed liquid falls from the horizontal pipe.
As it accumulates on the lower condensation heat transfer surface one after another,
This has the disadvantage that the overall performance deteriorates. Problems to be Solved by the Invention The present invention has been made in view of the problems of the prior art and to solve the problems. The purpose of the present invention is to provide a new high-performance vertical condensing heat exchanger tube having a structure that can perform the following tasks. Means for Solving the Problems In order to achieve this objective, the present invention develops inclined grooves cut deeper than the vertical grooves at an appropriate pitch in a heat transfer tube having fine vertical grooves, that is, a full-treaded tube. In addition, one or more drain gutters are provided to collectively discharge the condensate discharged along the inclined groove in the vertical direction, and further, on the downstream side of the inclined groove separated by the drain gutter, It is characterized in that a drain bar is provided along the side edge of the drain gutter. Embodiments Hereinafter, details of the present invention will be sequentially explained according to illustrated embodiments. In FIG. 1, a condensing heat exchanger tube 1 is composed of four elements. The first element is that it has fine vertical grooves 2 (flattened pipe), as shown in FIG. Second
The figure shows its cross section. The second element is that in order to eliminate the liquid film distribution in the axial direction, which is a major drawback of full-treaded pipes, the inclined grooves 3 are provided at an appropriate pitch p, and the condensed liquid condensed in the vertical groove portion 2 is quickly transferred to the inclined grooves. 3 to prevent the accumulation of a liquid film. Therefore, as shown in FIG.
It is necessary to dig the inclined groove 3 deeper than the depth of a.
It is desirable to have a structure that prevents the condensate from entering the vertical grooves 2 again, such as the cross-sectional shapes shown in FIGS. 3a and 3b. The third element is that a drain gutter 4 is provided to allow the condensate that has flowed into the inclined groove 3 to flow in the axial direction. The drain gutter 4 can be provided at one or multiple locations in the circumferential direction, but if more are provided, the heat transfer area will decrease, so the groove width l should be designed with this point in mind, as shown in Figure 2. There is a need to. The fourth element is that the drain bar 5 is provided along the side edge 4a of the drain gutter 4 on the downstream side of the inclined groove 3 divided by the drain gutter 4. Since the condensate flows into the drain gutter 5 from its inclined grooves 3, if it is used vertically, the liquid film will be considerably thicker in the lower part. Therefore, in order to prevent the condensate from flowing into the inclined groove 3 of the next pitch, the drain bar 5 is provided as described above. By appropriately selecting the width h and shape of the drain bar 5, the condensate can be efficiently drawn into the drain gutter 4, the width l of the drain gutter 4 can be reduced, and the effective area of the condensing heat exchanger tube 1 can be increased. In addition, the condensed liquid flows down along the drain bar 5 and plays the role of quickly separating the condensed liquid from the heat transfer tube 1. As the drain bar 5, 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 5 may have a shape that is narrow at the upper end and widened toward the lower end, for example. Effect of the invention Next, condensing heat exchanger tube 1 having the above basic structure
In order to explain the effect, an explanation will be given according to an experimental example. First, FIG. 4 shows a conceptual diagram of the experimental equipment system. In the figure, a vertical condenser 6 has an inner shell 7 therein, and has a structure in which steam is introduced from above. Condensing heat exchanger tube 1 of the present invention
is arranged at the center of the condenser 6 and can be connected to the outside of the condenser 6 so that the internal cooling fluid can flow in series. Here, 8 is a liquid storage tank, 9 is an evaporator, and 10 is a circulation pump. In this experimental device, working fluid vapor first flows into the condenser 6 from the line 11, and after the flow of the vapor is rectified by the inner shell 7, it is condensed on the surface of the condensing heat exchanger tube 1. The condensate is collected in a liquid storage tank 8 through a line 12, sent to an evaporator 9 through a line 13 by a circulation pump 10, and circulated again as vapor. A fluid whose temperature is lower than the steam temperature flows into the condensing heat transfer tube 1 from a line 14 and is returned to the outside of the system from a line 15. Here, the amount of exchanged heat of the condensing heat transfer tube 1 can be calculated from the flow rate, specific heat, and temperature difference between the inlet and outlet of the internal cooling fluid. In addition, the evaporator 9 uses a shell and tube type heat exchanger, and has a structure in which a fluid higher than the steam temperature flows through a line 16 and is discharged from a line 17.Similar to the condenser 6, the flow rate of the heated fluid is The amount of steam can be calculated from the specific heat and the temperature difference between the inlet and outlet. Now, using this experimental device, the condensing heat transfer performance of the condensing heat transfer tube of the present invention was measured. The test condensing heat exchanger tube is a condensing heat exchanger tube A of the present invention,
Measurements were made for three tubes: a full-treaded tube B and an ordinary bare (smooth) tube C with no surface treatment. The specifications of each tube A, B, and C are as follows, as an example.

[Table] The experiment was conducted using Freon 22 (R
-22), the experiment was conducted using cold water at 5-10℃ as the condenser cooling fluid and hot water at 28-35℃ as the evaporator heating fluid. The experimental results are shown in Figure 5. In the figure, the horizontal axis is the actual surface area standard (calculate the area of convex and concave parts)
heat flux (Kca/m ² h), and the vertical axis is the condensation heat transfer coefficient α _c (Kcal//m ² h) based on the real surface area.
°C). As a result, in the condensing heat exchanger tube A of the present invention,
A heat transfer coefficient of 4 to 5 times that of smooth tube C was achieved. In addition, since the heat exchanger tube A has a surface area approximately 1.9 times that of the smooth tube C, it is actually 80% according to the smooth tube C standard.
It is thought that the performance is approximately 10 times higher. In addition, in the full-treaded tube B, although the condensation heat transfer coefficient α _c is high in the region of low heat flux, in the region of 10,000 Kcal/m ² h or more (actual usage range) where the amount of condensation per tube increases, The heat transfer coefficient α _c rapidly decreases,
It is estimated that a large liquid film distribution is formed in the axial direction. Therefore, it is difficult to adopt long pipes of 4 m or more because the effect becomes significant. In this respect, the condensing heat transfer tube A of the present invention maintains high heat transfer performance even under high heat flux, and it is considered that even a long tube can exhibit sufficient performance. Note that the shape of the uneven portion of the full-treaded pipe, the width of the drain gutter, the width and shape of the inclined groove, and the height and shape of the drain bar can be selected to be the optimal shape that suits the conditions such as temperature and heat flux. Since the present invention provides high-performance condensing heat transfer, the number of heat transfer tubes can be reduced. For example, in low temperature difference power generation systems such as ocean temperature difference power generation, condensing heat transfer tubes are replaced with smooth tubes. It can be reduced to less than 2/1, and can greatly contribute to reducing the overall system cost by reducing piping and containment vessel dimensions.

[Brief explanation of drawings]

Fig. 1 is a front view of the condensing heat exchanger tube of the present invention, Fig. 2 is a sectional view taken along the line - - of Fig. 1, Fig. 3 a and b are enlarged longitudinal sectional views taken along the line - - of Fig. 1, and Fig. 4 is a condensing tube of the same. A conceptual diagram of the experimental equipment system for heat exchanger tubes. Figure 5 is a graph showing the experimental results in terms of the relationship between heat flux and condensing heat transfer coefficient. Figure 6 is a front view of a conventional condensing heat exchanger tube.
FIG. 7 is a sectional view taken along the line -- in FIG. 6. 1... Condensing heat transfer tube, 2... Vertical groove, 3... Inclined groove, 4... Drain gutter, 5... Drain bar.

Claims (1)

[Claims] 1. In a heat transfer tube having fine vertical grooves, that is, a full-treaded tube, inclined grooves are cut deeper than the vertical grooves at an appropriate pitch, and the condensate removed along the inclined grooves is collected and collected vertically. A condensing heat exchanger tube configured by having one or more drain gutters for discharging in the direction, and further providing a drain bar along the side edge of the drain gutter on the downstream side of the inclined groove divided by the drain gutter.