KR20190002090A - Corrugated tube for surface condenser - Google Patents

Abstract

According to the present invention, a corrugated tube for a surface condenser has three corrugations formed on a surface of the corrugated tube in the longitudinal direction, wherein a pitch of one corrugation is less than 0.5 compared to an inner diameter of the corrugated tube. According to the corrugated tube for a surface condenser, the number of corrugation formed on the surface of the corrugated tube in the longitudinal direction is designed by evaluating a change in an overall heat transfer coefficient with respect to the number of the corrugation to confirm the number of corrugation with the sharpest increase in the overall heat transfer coefficient under a plurality of conditions that differs a flow speed of cooling water flowing through the corrugated tube and pressure of steam supplied to the surface condenser, and then selecting the pitch and length of the corrugation.

Description

{Corrugated tube for surface condenser}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrugated tube for a surface concrete deck, and more particularly, to a corrugated tube for a surface concrete deck having a spiral wrinkle for promoting heat transfer on the surface of a plurality of pipes through which cooling water for liquefying steam in a surface condenser has flowed.

In a facility that uses a large amount of steam, such as a power plant, a condenser is needed to cool, liquefy and recover the steam used (eg, steam after turning the turbine) into water. This is because, since the water after liquefaction of the steam contains a considerable amount of heat, it is energy-efficient to produce steam by heating the high-temperature water again. For example, in a power plant, liquefied water is supplied to the steam generator through the condenser, and then heated again to steam.

The basic configuration of the condenser is shown in Fig. 1 includes a plurality of tubes 20 fixed to both tube sheets 10 so as to traverse the space inside the condenser 1 and a plurality of tubes 20, The steam 40 flows into the condenser along a direction perpendicular to the direction in which the steam 40 flows. The cold cooling water 30 flows through the plurality of pipes 20 and the steam 40 which is in contact with the outer surface of the cold multiple pipes 20 is liquefied by dropping the heat to a temperature below the boiling point.

The condenser having such a structure is referred to as a surface condenser 1, and the air mixed into the condenser 1 is discharged toward the ejector which is a vacuum system. For reference, the surface condenser 1 shown in Fig. 1 divides half of the space of the left tube sheet 10 into spaces for the inflow and outflow of the cooling water 30, The directions in which the cooling water 30 flows in the half of the plurality of pipes 20 are opposite to each other.

The structure itself of the surface condenser 1 is very simple and the action of liquefying the vapor 40 solely involves the cooling water 30 through the surface of the plurality of pipes 20 and the high temperature steam 40, Lt; / RTI > Therefore, the efficiency of the surface condenser 1 is greatly influenced by the design of the plurality of pipes 20. [ If it is possible to improve the performance of the surface condenser 1 by designing the plurality of pipes 20 well, it is possible to improve the surface condenser 1 by itself and, on the other side, to keep the performance of the condenser 1 the same It is very important to optimize the design of the plurality of pipes 20. [

Korean Patent Publication No. 2017-0065896 (published on June 14, 2017)

It is an object of the present invention to provide a corrugated tube for a surface concrete device capable of suppressing or reducing a pressure drop while promoting heat transfer and condensation of steam through the surface, thereby improving the efficiency and performance of the surface condenser.

The present invention relates to a corrugated pipe used as a plurality of pipes provided in a surface condenser, wherein the number of corrugations formed on the surface along the longitudinal direction of the corrugated pipe is 3, and the pitch of the corrugation is 0.5 or less .

Further, the pitch and depth of the three wrinkles are 0.1 and 0.01, respectively, as compared with the inner diameter of the bellows.

Here, the inner diameter and thickness of the corrugated pipe are 21 mm and 1.0 mm, respectively, and the ratio of the pitch and depth of the three corrugations to the inner diameter of the corrugated pipe is maintained within the inner diameter and thickness range of the corrugated pipe.

The inner surface and the thickness of the corrugated pipe according to the present invention are 21 mm and 1.0 mm, respectively, and the pitch and depth of the three corrugations may be 2.1 mm and 0.2 mm, respectively.

Further, the present invention is characterized in that the number of corrugations formed on the surface along the longitudinal direction of the corrugated tube is set to a total number of corrugations under a plurality of conditions that differ in the flow rate of the cooling water flowing through the corrugated tube and the pressure of the steam supplied to the surface condenser The number of the corrugations having the largest increase in the overall heat transfer coefficient is firstly determined and the pitch and depth of the corrugations are then selected by evaluating the change of the heat transfer coefficient do.

Here, the number of the corrugations having the largest increase in the overall heat transfer coefficient is three.

Further, the pitch and the depth of the three corrugations of the corrugated tube for surface condenser are respectively 0.1 and 0.01 with respect to the corrugated tube inner diameter.

Here, the pitch and depth ratios of the three wrinkles to the inner diameter of the bellows are maintained within the inner diameter and thickness range of the bellows to which similarity is recognized.

As described above, according to the present invention, it is confirmed that the design factor to be fixed as the first priority in the design of the corrugated tube for a surface complex device lies in the number of corrugations, and by fixing the number of corrugations to the highest priority, And the effort and time to enter has been reduced to 1/4 to 1/3 of the conventional level.

Also, through the improved design technique of surface corrugated tube, the overall heat transfer coefficient has been improved to the greatest, and the optimal specification of the corrugated tube for surface condensation has been obtained.

In this case, when the corrugated tube having a large overall heat transfer coefficient while suppressing the increase in the pressure drop is applied to the surface condenser, the size of the surface condenser can be drastically reduced while maintaining the same performance as the conventional condenser, And so on.

1 is a view showing an example of a surface condenser;
Fig. 2 shows the main design parameters of a corrugated tube to be applied to a plurality of tubes of a surface condenser. Fig.
FIGS. 3 to 7 are graphs for quantitatively evaluating changes in the overall heat transfer coefficient with respect to the number of corrugations under various conditions that are different from the flow rate of the cooling water flowing through the corrugated tube and the pressure of the steam supplied to the surface condenser.

Hereinafter, embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; coupled "or" connected "indirectly.

The present invention relates to a plurality of pipes through which cooling water flows in a surface condenser, and more particularly to a corrugated tube (100) in which at least one wrinkle that rises in a spiral manner along the longitudinal direction is formed on the surface. Wrinkles formed on the surface of the plurality of tubes increase the heat transfer area and generate turbulence locally, thereby promoting heat transfer. As a result, it plays a role of improving the over-all coefficient of heat transfer to a certain degree.

The evaluation of the heat transfer performance of the corrugated tube 100 for surface concrete use by the overall heat transfer coefficient is based on the fact that the heat transfer from the external steam through the corrugated tube 100 to the internal cooling water takes place at the inner and outer walls of the corrugated pipe 100 This is because the heat transfer coefficient affects the total heat transfer rate.

In addition, a factor necessary for evaluating the performance of the corrugated tube 100 for the surface complex is the pressure drop. When there are spiral concave grooves like the corrugated pipe 100 compared to the smooth surfaces of the plurality of pipes, the uneven surface shape acts as a resistance to the cooling water flowing in the corrugated pipe 100, which inevitably causes the pressure to drop. If the pressure drop is large, the power for maintaining the proper flow rate of the cooling water is consumed more, or the length or diameter of the corrugated pipe 100 should be made larger than the case of applying a smooth pipe.

As a consequence, the pressure drop is advantageous as it is smaller than the overall heat transfer coefficient. Designing a suitable corrugated pipe 100 is not an easy task because the pressure drop and the overall heat transfer coefficient are generally in a trade-off relationship.

Fig. 2 shows three design factors related to wrinkle formation in the corrugated tube 100 for surface complex devices. The three design factors relate to the number of wrinkles (N, the number of wrinkle start points), the pitch (P) between the wrinkles, and the depth of the wrinkles (D).

Three design factors are important for designing one corrugated tube 100 in the surface condenser, and both the overall heat transfer coefficient and the pressure drop in the tradeoff relationship as performance evaluation factors of the surface corrugated tube 100 It is considerably difficult to design the optimum corrugated pipe 100. [0051]

In addition, another difficulty in designing the corrugated tube 100 for a surface complex is that it is difficult to simulate by computerization, that is, to simulate. This is due to the fact that it is currently difficult to compute mathematically the complex physical phenomenon accompanied by a phase change in which the vapor is liquefied with water on the outer surface of the corrugated tube 100 of the surface condensate. Therefore, the design of the corrugated tube 100 for a surface complex is currently required to involve a considerable combination of experiments, which needs to be solved.

The present invention aims to provide a method for efficiently designing the corrugated pipe 100 in terms of time and cost as well as deriving the optimum corrugated pipe 100 in designing the corrugated pipe 100.

Firstly, three important design factors regarding the wrinkle formation of the surface crepe tube 100 above are mentioned. Incidentally, one more thing concerns the dimensions of a smooth multiple tube on which wrinkles are formed. A plurality of commonly used pipes have an outer diameter of 19 to 24 mm and a thickness of about 0.55 to 1.3 mm. Typical dimensional-related information for multiple tubes of surface condensers is provided in A. Nirmalkumar P.Bhatt, BAM Lakdawala, CVJ Lakhera, "Steam Surface Condenser Design Based on Cost Optimization using Genetic Algorithm, INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD, DECEMBER, 2011 ".

In the present invention, simulations and experiments were carried out on specimens having a smooth inner diameter of 21 mm and a thickness of 1.0 mm. The pitch (P) and depth (D) of the wrinkles were measured in the inner diameter (Note that the number of natural wrinkles is not expressed as a ratio). Here, an inner diameter of 21 mm and a thickness of 1.0 mm means a representative value covering all smooth tubes having an inner diameter and a thickness in the range of 20.5 to 21.4 mm and 0.95 to 1.04 mm, respectively, .

The present invention is based on three important design factors related to the wrinkle formation of the corrugated pipe 100 that need to be determined first, that is, the number of wrinkles (N , Number of wrinkle starting points) were selected. This is because the number N of wrinkles has the greatest effect on the shape difference when viewed in the whole corrugated pipe 100 and thus is considered to be a general factor having a dominant influence on the overall heat transfer coefficient and the pressure drop.

3 to 7 are quantitative evaluations of changes in the overall heat transfer coefficient with respect to the number of corrugations N under various conditions, which are different from the flow rate of the cooling water flowing through the corrugated pipe 100 and the pressure of the steam supplied to the surface condenser. Of course, the pitch P and depth D of the pleats are the same in all cases.

Surprisingly, the overall heat transfer coefficient was overwhelmingly superior to the case of three wrinkles (N) under certain flow conditions and steam pressure conditions. That is, it was confirmed that the overall heat transfer coefficient decreased sharply compared with the case where the number of wrinkles (N) was less than or greater than three. Therefore, based on such a large number of evaluations, the number of wrinkles (N) was first determined to be three. Here, the ordinate of the graphs of FIGS. 3 to 7 is expressed as an increase in overall heat transfer coefficient, and the criterion for the increment calculation is the overall heat transfer coefficient in a plurality of pipes with smooth surfaces without wrinkles.

Next, the number of wrinkles (N) was fixed to three, and then the pitch (P) and depth (D) of the wrinkles were variously changed, and then the overall heat transfer coefficient and the increase in the pressure drop were experimented.

Table 1 below summarizes the experimental results obtained by variously changing the pitch (P) and depth (D) of the wrinkles with the number of wrinkles (N) fixed at three. For reference, as described above, the inner diameter and the thickness based on smooth tubes are 21 mm and 1 mm, respectively.

Experimental results in which the number of wrinkles (N) was fixed to 3 and the pitch (P) and depth (D) of the wrinkles were variously changed No
Pitch / depth
(Mm) Pitch / depth
(Ratio to inner diameter) Overall Heat Transfer Coefficient Increase (%) Increase in Pressure Drop (%) Heat transfer coefficient inside Out One 2.1 / 0.2 0.1 / 0.01 141 132 0.0292 1.896 2 6.4 / 0.2 0.3 / 0.01 132 144 0.0331 1.216 3 8.7 / 0.4 0.4 / 0.02 127 157 0.0359 1.017 4 22.1 / 0.2 1.1 / 0.01 111 106 0.0279 0.987 5 22.1 / 0.6 1.1 / 0.03 119 125 0.0354 0.883

In the above experimental results, if the pitch P is 22.1 mm, which is almost equal to the inner diameter of the corrugated pipe 100, the increase in pressure drop is the smallest, but the increase in the overall heat transfer coefficient is almost equal to the increase in pressure drop It can be confirmed that the substantial improvement effect is insignificant.

When the experimental results with shorter pitch (P) are narrowed down to candidates, the largest specification of the increase in overall heat transfer coefficient is the first one with the groove pitch (P) / depth (D) of 2.1 / 0.2 (mm) It can be confirmed that it is the corrugated pipe 100. Also, the corrugated tube (100) of the first specification has the largest increase of the overall heat transfer coefficient (141%), while the increase of the pressure drop is 132% smaller than the increase. This is a very encouraging result for the second and third specifications when compared to the increase in pressure drop over the overall heat transfer coefficient increment.

As described above, it is difficult to predict the overall heat transfer coefficient and the change in the pressure drop due to the change of the pitch (P) and depth (D) of the corrugation, and it is almost impossible to analyze the phase change phenomenon occurring on the outer surface of the corrugated pipe Therefore, in order to actually design the corrugated tube 100 for an actual surface complex, there are many parts that must be directly tested. This makes the design of the corrugated tube 100 for a surface complex device difficult.

However, in the present invention, the number N of wrinkles has the greatest influence on the difference in shape when viewed in the whole corrugated pipe 100, and thus the number N of corrugations has a dominant influence on the overall heat transfer coefficient and the pressure drop. 3 to 7, it is assumed that the number N of corrugations is smaller than the number of corrugations N under various conditions, which is different from the flow rate of the cooling water flowing through the corrugated pipe 100 and the pressure of the steam supplied to the surface condenser, It is confirmed that the improvement of the overall heat transfer coefficient is dramatically improved in three cases.

As described above, according to the present invention, it is confirmed that the design factor to be fixed as the first priority in the design of the corrugated tube 100 for surface complex is at the number of corrugations N, and the number N of corrugations is fixed to the highest priority The effort and time required for the entire designing of the corrugated tube 100 for a surface complex device can be reduced to 1/4 to 1/3 of the conventional one.

In addition, through the improved design technique of the corrugated tube 100 for surface complex devices, the overall heat transfer coefficient is improved to the greatest, and the optimum pressure gauge tube 100 for the surface islands is obtained.

As described above, when the corrugated tube 100 having a significantly improved overall heat transfer coefficient while suppressing an increase in the pressure drop is applied to the surface condenser, the size of the surface condenser can be drastically reduced while maintaining the same performance as in the prior art. It is possible to expect various benefits such as a reduction in the number of users.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

1: surface condenser 10: tube sheet
20: Multiple pipes 30: Cooling water
40: steam 100: corrugated tube
N: number of wrinkles P: pitch of wrinkles
D: Wrinkle depth

Claims (8)

In a corrugated pipe used as a plurality of pipes provided in a surface condensate,
Wherein the number of corrugations formed on the surface of the corrugated tube along the longitudinal direction of the corrugated tube is 3 and the pitch of the corrugation is 0.5 or less of the corrugated tube inner diameter. The method according to claim 1,
Wherein the pitch and depth of the three corrugations are 0.1 and 0.01, respectively, with respect to the corrugation inner diameter. 3. The method of claim 2,
Wherein the inner diameter and thickness of the corrugated tube are 21 mm and 1.0 mm, respectively, and the pitch and depth ratio of the three corrugations to the inner diameter of the corrugator tube are maintained within the inner diameter and thickness range of the corrugated tube, Crease tube for multiple devices. 3. The method of claim 2,
Wherein the inner diameter and the thickness of the corrugated pipe are 21 mm and 1.0 mm, respectively, and the pitch and depth of the three corrugations are 2.1 mm and 0.2 mm, respectively. A method of designing a corrugated pipe for use in a plurality of pipes provided in a surface condensate,
The number of corrugations formed on the surface of the corrugated tube along the longitudinal direction of the corrugated tube may be changed by a change in the overall heat transfer coefficient with respect to the number of corrugations under a plurality of conditions that are different from each other in the flow rate of the cooling water flowing through the corrugated tube and the pressure of the steam supplied to the surface condenser The number of the corrugations having the largest increase in the overall heat transfer coefficient is first determined,
And then selecting the pitch and depth of the corrugation. 6. The method of claim 5,
Wherein the number of corrugations having the largest increase in the overall heat transfer coefficient is three. The method according to claim 6,
Wherein the pitch and depth of the three corrugations of the corrugated tube for surface condensation are 0.1 and 0.01, respectively, with respect to the corrugated tube inner diameter. The method according to claim 6,
Wherein the pitch and depth ratio of the three wrinkles to the inner diameter of the bellows tube are maintained within the inner diameter and thickness range of the bellows to which similarity is recognized.

Images