JPS62280505A - Feedwater heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a feed water heater for thermal power and nuclear couplants,
This invention relates to a feed water heater that has greatly improved heat exchange performance by reducing pressure loss within the shoulder body and stabilizing the bottom drain water level.

[Prior art]

As described in Japanese Patent Application No. 58-35395, a conventional feed water heater for a thermal power or atomic couplant has a structure in which tube support plates are alternately installed above and below, and steam flows in a meandering manner within the body. This structure had a problem in that the pressure loss on the steam side was large and the heat exchange performance was significantly reduced.

An example of a feed water heater according to the prior art will be described with reference to FIG. In the figure, the water supply enters the water chamber 1 from the water supply inlet nozzle 2, passes through the U-shaped heating pipe 5, and is sent out from the water supply outlet nozzle 3. A plurality of the U-shaped heating tubes 5 are provided to form a tube group, and penetrate through the tube plate 4 into the water chamber 1.
It is open to the body 9 and supported by tube support plates 6, 6' and tie rods 7. Tube support plates 6,6' are placed one above the other and have the role of supporting the tube group and guiding the steam flow path so that it becomes a meandering flow. Therefore, the heated steam extracted from the turbine enters the vessel from the steam inlet nozzle 1o, becomes a flow divided into two in the longitudinal direction of the fuselage, and flows to each terminal vent outlet 8, 8'. These heated steam comes into contact with the surface of each tube 5 of the tube group, exchanges heat with the feed water flowing through the tubes, condenses, becomes drain 12 and accumulates at the bottom of the vessel, and drains through drain outlet 14.
is discharged from.

In the feedwater heater with the conventional structure described above, a large amount of steam, which is about half of the steam inflow, flows into the tube nests at the front and rear of the fuselage, resulting in a large pressure loss on the steam side, resulting in a decrease in the internal pressure and a decrease in the lower fuselage drain. A water level gradient position 5 is generated.

In the temperature diagram shown in Fig. 9, the decrease in pressure inside the vessel causes the bleed pressure to drop from the saturation temperature TS to the saturation temperature TS' with respect to the original pressure, reducing the temperature difference with the feed water heater. Since the heat capacity is proportional to the logarithmic average value of this temperature difference, a decrease in the internal pressure causes a decrease in the performance of the feed water heater. Therefore, it is effective to reduce pressure loss as much as possible to improve performance. In addition, the occurrence of a water level gradient in the lower fuselage drain causes the heating tube to be submerged in water at locations where the water level is high, reducing the heating area, which causes a decrease in the internal pressure and a decrease in the performance of the feedwater heater.

In order to eliminate these performance deterioration factors, efforts have been made to adopt a parallel flow that distributes the steam evenly to each tube nest section instead of making it a meandering flow. It was found that due to the inertial force of the area, it collided with the bottom of the fuselage directly below the steam inlet, causing an increase in pressure loss and a water level gradient.

The increase in pressure loss and the generation of a water level gradient due to inertial force when steam flows in will be explained with reference to FIGS. 5 and 6.

@Figure 5 shows the steam pipe stand 1 as already mentioned in Figure 4.
Pipe support plate 6 so as to meander the heated steam introduced from 0
, 6' are schematically arranged in such a way that they are alternately arranged vertically. Reference numeral 11 denotes an impact prevention plate provided to prevent heated steam from directly colliding with the heat exchanger tubes 5.

FIG. 6 schematically depicts a feed water heater modified from the parallel flow type described above.

[Problem that the invention attempts to solve]

As shown in FIG. 6, heated steam flows into the body from the steam inlet nozzle 10, and its flow velocity is as high as 50 to 60 m/s. Since the amount of steam consumed by each tube nest section 16 is fixed, it was thought that once the steam entered the fuselage, it would be quickly distributed in the longitudinal direction of the fuselage and absorbed into each tube nest. As a result of a steam flow experiment, it was found that due to the inertial force caused by the high speed of 50 to 60 m/s when steam flows in, nearly the entire amount of steam 17 flows into tube nest section 1 directly below the steam inflow point.
It was found that after entering the 1M4 body and colliding with the lower part of the 1M4 body, it was redistributed to each tube nest section. Furthermore, due to this phenomenon, the pressure loss inside the fuselage increases, and the drain water level directly below the steam inlet drops locally, causing the water level in other locations to rise, causing a portion of the heating tube to be submerged. found.

The present invention was made based on the above research results, and prevents the adverse effects of the inertia of the introduced high-speed steam flow, thereby locally lowering the drain directly below the steam inlet and raising the drain water level in other locations. It is an object of the present invention to provide a feed water heater that is safe and has less pressure loss in the body.

[Means for solving problems]

Compared to the meandering flow type shown in Fig. f55, the parallel flow type shown in Fig. 6 has less pressure loss in the body, but it has a noticeable problem of pushing down the drain water level directly below the heating steam inlet. The present invention changes the cross-sectional area of the steam flow path on the side of the tube nest based on the assumption that the above-mentioned phenomenon of pushing down the drain water level is caused by heated steam flowing into the closed chamber of the tube nest. I did an experiment.

Value of the cross section of the flow path (ratio to the cross-sectional area of ITFJ)
It was discovered that when the above conditions were met, the pressure loss was significantly improved. This law will be described in detail below with reference to FIGS. 7 and 8.

Parallel hatched part 30 in Figure 7 (fuselage internal cross section '!1t excluding tube group 31 and drain 32) is set to parameter A3.
It is called. FIG. 8 Steam passage hatching part 33 (pipe support plate 6
and the internal cross-sectional area of the fuselage excluding the drain 32) is defined as parameter A.
Call it 4. Ratio α of A4 and A3 = A 4 / A
As a result of experiments, it was found that a is related to an increase or decrease in pressure loss.

FIG. 10 shows an example of the experimental results. It can be seen that the pressure increases near the point directly below the steam inflow point (indicated by the arrow), and a pressure gradient occurs at other points. Note that the amount of pressure fluctuation increases as the aforementioned parameter (α = A4/Aδ) is smaller, and decreases as the α value increases, and as the α value increases, that is, the steam side passage area A4 increases, the pressure loss is alleviated. I understand that. Therefore, in order to find an economically appropriate value for the α value, we organized the relationship between the α value and the pressure loss as shown in Figure 11, and found that when the α value is set to approximately 0.24 or more, the pressure loss is largely eliminated. It turned out.

Therefore, it can be seen that in order to determine the optimum body diameter that can sufficiently reduce the pressure loss for a given feed water heater tube nest, it is sufficient to design it by considering α=0.24.

Note that the ratio of the body length and body diameter of feed water heaters in conventional thermal and nuclear power plants is generally about 5 to 8 times, and the side steam flow path ratio is about 0.1 to 0.17. , the condition α=0.24 is applicable in these cases.

In addition, in order to install as many heating tubes as possible in the body of the feed water heater considering economic efficiency, the outer periphery of the tube nest is generally configured in a cylindrical shape along the inner diameter of the body.

For this reason, the steam passage area on the outer periphery of the tube nest is reduced, and in addition, the steam passage area is further reduced by the tube support plate, so the side steam passage ratio is conventionally 4:0.10. -0
．． 17 (10% to 17%).

The feed water heater under these conditions has a side steam flow path ratio α=0.24.
(24%) or more, a high-performance feed water heater with extremely low in-shell pressure loss, which is the desired effect of the present invention, can be obtained.

[Effect]

As described above, if the side steam flow path ratio is made larger than the conventional one, the flow rate of the side steam flow 34 in FIG. 6 becomes large. If you set this flow rate appropriately.

When steam inflows from the steam inlet and flows into the tube nest section directly below the steam inlet, the steam is moved and distributed to the side passages with sufficient area before increasing the dynamic pressure, resulting in a pressure loss. This eliminates the increase in water level as well as the increase in water level gradient, making it possible to adopt a parallel flow structure which significantly improves performance efficiency.

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of the same.

As shown in FIG. 1, a group of tubes 31 is installed in the body 9 of the feed water heater, and in the upper part of the group of tubes 31, in order to prevent the heating tubes from being damaged by the steam flowing in from the steam inlet nozzle holder 10. A shock prevention plate 11 is installed.

A vent plate main pipe 2o is provided at the center of the tube nest, and serves as the terminal end of the steam that has flowed into the tube nest, and serves to collect and discharge non-condensable gas. A vent guide baffle 21 is attached to the vent main pipe, and serves to reliably guide steam and non-condensable gas to the vent main pipe. With this vent extraction structure, the vent is completely discharged without stagnation in the tube cavity, contributing to improved performance. A notch 22 is provided on the outer periphery of the tube support plate 6 to quickly distribute steam flowing into the tube bundle section to each tube bundle section in the longitudinal direction, thereby preventing pressure loss from increasing. Including the tube support plate outer circumferential notch 22, the side steam flow path ratio is 24% or more (approximately 30% in this example).

As shown in FIG. 2, a parallel flow type feed water heater is constructed by arranging a plurality of tube support plates 6 at equal heights. A steam flow section 23 is formed in the upper part of each tube nest section 16. A portion of the steam flow is distributed to each tube nest section 2.
4, each tube nest section has a tube nest partial flow 2.
5, a portion of the steam flow is supplied, allowing operation with less pressure loss.

FIG. 3 shows a different embodiment from the above. In the feed water heater of this example, the tube nest shape is arranged in a rectangular shape in order to further secure a sufficient side steam flow path. With this configuration, it is easy to increase the area of the side passage.

A trial calculation example in which performance is improved by a design example in which the steam side flow path ratio α is o, 24 or more will be described below.

FIG. 9 shows a temperature diagram of a conventional feed water heater.

The feed water flows in at a temperature T1 and flows out of the vessel at a temperature T2. The water supply flow rate is GW, and the steam side maintains a constant temperature at the saturation temperature TS relative to the saturated pressure inside the fuselage. In the feed water heater under these conditions, the required heating area is 5ex(n(
) is expressed by the following formula.

KCKo■ Here, h2: Enthalpy corresponding to outlet water supply temperature tz (KcaQ/kg) hl: Enthalpy corresponding to inlet water supply temperature tl (K
can / kg) Kcze thermal conductivity (Kca Q / rd h ”C
) θ,: Logarithmic average temperature difference ('C) Also, 2, 3 Q og (Ts' - t 1) / (Ts
'tz), and the required heating area Scz is inversely proportional to the logarithmic average temperature difference θ. Furthermore, as shown in the above equation, θ increases due to an increase in the chamber saturation temperature Ts' (the saturation temperature of the pressure obtained by subtracting the pressure loss from the extraction pressure from the turbine), so the required heating area is reduced by reducing the chamber pressure loss. It becomes possible to decrease.

An example of performance comparison between a conventional type and a new type with an α value of 0.24 or more is shown below as an example of an atomic couplant feed water heater.

Oil vapor pressure (kg/an"a): 0.4 Water supply amount (ton/hr): 2200 Water supply temperature ("C): 48.3/71.2 As mentioned above, α=0. 3, the heating area (heat exchanger tube area) was reduced by 12%.

〔Effect of the invention〕

As detailed above, when the present invention is applied, the pressure loss of the heated steam in the feed water heater is reduced, and the drop in the drain water level directly below the heated steam inflow section and the occurrence of problems associated with this can be prevented. I can do it.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the invention. FIG. 1 is a cross-sectional view, and FIG. 2 is a longitudinal cross-sectional view. FIG. 3 is a cross-sectional view of an embodiment different from the above. FIG. 4 is a cross-sectional view of a conventional feed water heater. FIG. 5 is an explanatory diagram of a meandering flow type feed water heater, and FIG. 6 is an explanatory diagram of a parallel flow type feed water heater. FIG. 7 and FIG. 8 are explanatory diagrams of the side flow passage ratio. FIG. 9 is a temperature diagram for explaining the functions and effects of the embodiment. FIGS. 10 and 11 are charts for explaining the influence of the uneven flow path ratio. 5... U-shaped heating tube, 6... Pipe support plate, 7... Tie rod, 8... Terminal vent discharge 0.10... Steam inlet nozzle stand, 15... Water level gradient, 16... ...Each tube nest section, 17...Steam, 18...Lower steam flow path, 1
9... Closed room, 20... Vent removal main pipe, vent guide buckle, 22... Notch in pipe support plate, 2
3... Steam flow section, 24... Distribution flow, 25... Tube bundle side flow, 31... Tube group, 34... Side steam flow path section.

Claims (1)

[Claims] 1. A body having an inlet for introducing heated steam and a drain outlet, a plurality of U-shaped heat exchanger tubes provided in the body in the longitudinal direction thereof, and supporting the U-shaped heat exchanger tubes. In a feed water heater having a pipe support plate, at least a part of the periphery of the pipe support plate is provided with a notch for allowing steam to pass through, and a) an area obtained by subtracting the portion occupied by the drain from the internal cavity area of the vertical cross section of the body; is A_δ, b, the area obtained by subtracting the area occupied by the drain from the gap area between the inner surface of the body and the tube support plate is A_4, and the above A_4/A is
A feed water heater characterized in that a ratio α of _δ is set to 0.24 or more.