JP2963586B2 - Steam generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger and, more particularly, to a body side fluid rectification structure of a heat exchanger suitable for use in a steam generator of a liquid metal fast breeder reactor.

[0002]

2. Description of the Related Art FIG. 5 shows a helical coil type and FIG. 6 shows a straight tube type of a conventional large steam generator for a fast breeder reactor.

In the helical coil type steam generator 1 shown in FIG. 5, high-temperature liquid metal sodium as a body side fluid as a heating medium passes through a sodium inlet nozzle 3 provided on the upper part of the body 2 of the steam generator. It flows into the body 2 of the steam generator. This sodium descends on the outside of the helical coil tube bundle 7 formed by winding a plurality of heat transfer tubes 6 in a helical coil shape in an annulus space surrounded by a cylindrical inner cylinder 4 and an outer cylinder 5, It flows out of the body 2 from the outlet nozzle 8.

On the other hand, the water supply flows into a water supply inlet chamber 10 from a water supply inlet nozzle 9 provided below the body 2, is guided into a plurality of heat transfer tubes 6, and rises up the helical coil tube bundle 7.
At this time, the feedwater that has flowed in at a low temperature exchanges heat with the high-temperature sodium flowing outside the heat transfer tube 6, is preheated, boiled, and superheated, becomes high-temperature and high-pressure superheated steam, reaches the steam outlet chamber 11, and reaches the steam outlet nozzle 12 To a turbine (not shown).

In the straight tube type steam generator shown in FIG. 6, both open ends of a plurality of straight tube heat transfer tubes 6 are connected to a feed water inlet tube plate 19 or header and a steam outlet tube plate or header 20, respectively. A water supply inlet chamber 10 is provided in this water supply inlet tube sheet 19, a steam outlet chamber 11 is provided in a steam outlet tube sheet 20 part, and a body 2 is provided outside the tube bundle group 7 of straight pipes. Outlet tube sheet 20
To form a flow path for the body-side fluid. Like the helical coil type steam generator 1, high temperature liquid metal sodium as a heating medium passes through a sodium inlet nozzle 3 provided on the upper part of the body 2 of the straight tube type steam generator, and the steam generator 1
And flows down the tube bundle flow path composed of the plurality of straight tube heat transfer tubes 6 and the body 2, and flows out of the body from the sodium outlet nozzle 8.

On the other hand, the water supply is guided from the water supply inlet chamber 10 provided at the lower end of the body 2 to the plurality of heat transfer tubes 6 via the water supply inlet tube plate 19, rises up the straight tube bundle portion, and is outside the heat transfer tubes 6. Exchanges heat with the high-temperature sodium flowing through the pipe, is preheated, boiled, and superheated, becomes high-temperature and high-pressure superheated steam, is collected at the steam outlet tube sheet 20, and then reaches the steam outlet chamber 11, where the steam outlet nozzle 1
2 to a turbine (not shown).

[0007] Among the water-side flow systems of the steam generator 1 of the fast breeder reactor, the through-flow system includes a separated type and an integrated type. The separation type is configured such that an evaporator and a superheater having the same structure as the above-described steam generator 1 are separated, and the evaporator heats feed water with sodium to produce saturated steam or superheated steam having a slight degree of superheat. The generated superheater further heats the steam generated in the evaporator with hot sodium to generate hot superheated steam. On the other hand, the integrated type heats feedwater with high-temperature sodium by itself and directly generates high-temperature, high-pressure superheated steam.

[0008] In such a steam generator 1 structure, the drift generation of the body side fluid not only causes the performance of the steam generator 1 to deteriorate, but also causes a local temperature distribution at the steam outlet portion, and Causes the occurrence of defects such as impairing the structural integrity of the vehicle.

Therefore, the following measures have been taken in the conventional steam generator 1.

In the straight tube type steam generator, since the rectifying effect in the tube bundle 7 is smaller than that in the helical coil type steam generator, the baffle plate 16 is attached to the tube bundle 7 at regular intervals to suppress drift. The baffle plate 16 is installed at an appropriate interval even in the case of an integral flow-through type having a long length of the tube bundle 7 to cope with the problem. In addition, a dummy tube 17 is provided in a region near the outer cylinder where the heat transfer tube 6 cannot be disposed due to structural limitations, and an excessive gap formed by the outer tube 5 and the heat transfer tube 6 in the vicinity thereof is provided. However, there is no rectification effect on the entire tube bundle 7, and the baffle plate 16 rectifies or mixes the body side fluid.

On the other hand, in a helical coil type steam generator,
Since each heat transfer tube 6 is wound up in a helical coil shape, it is substantially perpendicular to the flow direction of sodium, and the tube bundle itself has a uniform resistor function, that is, a rectifying function. As additional measures, the optimization of the structure of the sodium distribution device and the installation of a rectifier above the tube bundle have been studied as countermeasures.

[0012]

However, in the case of the integral once-through type steam generator 1, the tube bundle 7 has a longer length than the separated once-through type, so that the potential for the occurrence of drift is high, and The following tendency tends to be generated because the steam having a large degree of superheat is generated by the method.

[0013] From the well-known phenomenon that the superheat degree of the outlet steam is larger than that of the separation type and that the water tends to oscillate if the superheat degree is large, the potential of the unstable flow generation on the water side is high.

When the steam generator 1 is started, the water-side outlet is heated by sodium and changes from a single-phase water to a two-phase state and superheated steam. However, since the degree of superheat of the outlet steam is large, each of the heat transfer tubes 6 If the shift from the two-phase state to the superheated steam occurs at the outlet, a large temperature difference occurs in the tube sheet, which may have an impact on structural integrity.

As a countermeasure for the straight tube type steam generator, a baffle plate 16 is added at the tube bundle portion 8 and a flow hole 18 for passing sodium through the baffle plate 16 is devised to improve the sodium content. Is adopted as a zigzag flow to promote mixing.

On the other hand, in the helical coil type, as a measure for suppressing the drift of the body-side fluid, a method of reducing the arrangement interval of the heat transfer tubes 6, reducing the area of the body-side flow path, and increasing the flow resistance can be considered. However, in consideration of a sodium-water reaction accident, a reduction in the interval between the heat transfer tubes 6 causes an increase in the scale of damage caused by the sodium-water reaction. There are restrictions. Further, it is structurally difficult to mount a rectifier having a conventional structure such as a baffle plate 16 inside the helical coil tube bundle 7. Therefore, a direct sodium rectifier in 7 parts of a long tube bundle has not been studied.

A first object of the present invention is that the tube bundle 7 is long,
In addition, it minimizes the drift of the body side fluid of the helical coil type steam generator of the integral once-through type with a large degree of superheat of the outlet steam,
Performance and structural integrity.

A second object of the present invention is to improve uniformity of the body-side flow path and improve the rectification effect.

[0019]

The first means of the present invention is as follows.
In order to achieve the first object, a plurality of heat transfer tubes through which the medium to be heated flows are formed in a spiral layer having a constant diameter,
Further, a heat transfer tube group in which spiral layers in which a plurality of other heat transfer tubes are wound outside or inside the spiral layer are concentrically combined, and a header to which the ends of the heat transfer tube group are connected, It comprises a cylindrical inner cylinder installed concentrically at the center of the spiral of the spiral heat transfer tube group, an outer cylinder installed concentrically outside the spiral heat transfer tube group, and a body enclosing the outer cylinder. In the steam generator, in one or more cross sections in the direction perpendicular to the axis of the heat transfer tube group, a resistor is provided in the tube bundle axial direction in parallel with the helical layer for each body-side flow path surrounded by the helical layer adjacent thereto. It is characterized by being installed.

In order to achieve the second object, the second means is the above-mentioned first means, wherein the body is constituted by the spiral heat transfer tubes adjacent to each other of the spiral layers adjacent to each other. A resistor having the same inclination angle as that of the spiral heat transfer tube at an intermediate curvature between the curvatures of the adjacent spiral layers for each fluid flow path region is installed in parallel with the spiral layer. It is assumed that.

[0021]

According to the first means, the flow area of the body-side fluid in a predetermined area in the helical coil tube bundle 7 can be reduced. The side pressure loss value increases. For this reason, the dynamic pressure distribution due to the drift generated on the upstream side of the region is reduced and rectified.

According to the second means, the flow path shape of the body-side fluid in the cross section of the helical coil tube bundle 7 can be made uniform, and the rectifying effect can be increased.

[0023]

FIG. 1 shows an embodiment of the present invention. 1 which are the same as those in FIG. 5 are denoted by the same reference numerals. Further, a heat transfer tube support device 15 shown in FIG. 2 described below is not shown for convenience. This figure shows the (a) horizontal cross section and (b) axis of the helical coil tube bundle 7 when the present invention is applied to the helical coil type steam generator 1 that performs heat exchange between sodium and water as the body side fluid. FIG. Each heat transfer tube 6 is wound up at a constant pitch in the axial direction in each helical coil layer. The pitch of the heat transfer tubes 6 in the radial direction of the steam generator, that is, the interval between the helical coil layers installed concentrically is constant. In the present embodiment, in the middle part of the helical coil tube bundle in the height direction, a plate is provided concentrically with each helical coil layer so as not to be in contact with the heat transfer tube for each body side flow path which is an annulus space between the helical coil layers. Flow resistor 13 is provided. The resistor 13 is
It has a curvature that is intermediate between the curvatures of the adjacent spiral layers, that is, a curvature diameter that is intermediate between the diameters of the adjacent spiral layers.

When sodium flows in this region, the sodium flow path area in this region is smaller than that in the region where the resistor 13 is not provided, so that the flow velocity of sodium increases, and the unit length in the axial direction in this region is increased. The per-sodium pressure drop value is greater than in other regions. Therefore, when a drift occurs on the upstream side of the region, the dynamic pressure distribution corresponding to the sodium velocity distribution flows into the region, is flattened, and the sodium flow is rectified. Also, since the sodium flow path area per heat transfer tube 6 is also reduced at an equal rate,
After the rectification, heat exchange is performed in each heat transfer tube 6 at an equal flow rate of sodium and water, and as a result, the steam outlet of each heat transfer tube 6 of the steam generator 1 becomes uniform.

FIG. 2 is a top view of the helical coil tube bundle 7 to which the resistor 13 of this embodiment is attached. Each heat transfer tube
An annulus portion of the inner cylinder 4 and the outer cylinder 5, that is, supported by a heat transfer tube support device 15 radially installed in the body side flow path,
The sodium flow path, which is the body-side flow path, is divided into a fan shape by the heat transfer tube support device 15. The heat transfer tube supporting device 15 can be disassembled and disassembled in a radial direction or a radial direction as is known, and can support the heat transfer tubes of each layer. As shown in FIG. 3A, the resistor 13 is divided into the same number as the number of divided sodium channels, and both sides of the resistor 13 are connected to the heat transfer tube support device 15 by means of welding, bolting, fitting, or the like. Mounted parallel to the helical coil layer. The resistor 13
Is attached to the tube bundle supporting device 15 in order to absorb the difference in thermal expansion between the heat transfer tube 6 and the resistor 13 when the steam generator 1 is operated.
Although a slidable structure such as a structure may be used, it is not limited to an embodiment of the present invention.

FIG. 4 shows another embodiment of the present invention. This figure divides the resistor 13 of the invention shown in FIG.
Each of the resistors 14 has the same rod shape, and each of the divided resistors 14 is parallel to the helical coil heat transfer tube 6 at each central portion of a region surrounded by four adjacent heat transfer tubes 6 of the adjacent helical coil layer. And the resistor 14 is installed at the same inclination angle. In the present embodiment, the flow path cross section in the resistor 14 installation area is made uniform, and the flow on the sodium side is further made uniform. As shown in FIGS. 2 and 3 (b), the resistor 14 of this embodiment is also divided into the same number as the number of divided sodium channels, and both sides thereof are welded to the heat transfer tube supporting device 15 by bolts. The helical coil layer is attached in parallel with the helical coil layer by means such as stop and fitting. In each of the above embodiments, the resistor 13 is provided in one region in the helical coil tube bundle 7 part.
Although 14 is installed, resistors 13 and 14 are installed in a plurality of regions corresponding to the height of the tube bundle 7.

[0027]

According to the first aspect of the present invention, the flow area of the body-side fluid in a predetermined region in the helical coil tube bundle of the helical coil type steam generator can be reduced, so that the flow rate of the body-side fluid in this region is reduced. And the body-side fluid-side pressure loss value increases. For this reason, the body-side dynamic pressure distribution in the case where a drift occurs upstream of this region is reduced with the inflow into the region, and the flow of the body-side fluid is rectified.

According to the second aspect of the present invention, the shape of the flow path of the body-side fluid in the cross section of the helical coil tube bundle can be made uniform, and the rectifying effect can be increased.

[Brief description of the drawings]

FIG. 1A is a horizontal sectional view of a tube bundle in a helical coil type steam generator according to one embodiment of the present invention, and FIG.
Is an axial sectional view.

FIG. 2 is a partial view of the tube bundle of the helical coil type steam generator according to one embodiment of the present invention as viewed from above.

FIG. 3 is a diagram showing a resistor shape according to an embodiment of the present invention;
(A) is a figure which shows plate shape, (b) is a figure which shows rod shape.

4A is a perspective view of a part of a tube bundle in a helical coil type steam generator according to an embodiment of the present invention, taken in a horizontal cross section and viewed obliquely from above, and FIG. It is sectional drawing.

FIG. 5 is an axial sectional view of a conventional helical coil type steam generator.

FIG. 6 is an axial sectional view of a conventional straight tube steam generator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steam generator 2 ... Body 3 ... Sodium inlet nozzle 4 ... Inner cylinder 5 ... Outer cylinder 6 ... Heat transfer tube 7 ... Tube bundle part 8 ... Sodium outlet nozzle 9 ... Water supply inlet nozzle 10 ... Water supply inlet room 11 ... Steam outlet room 12 ... Steam outlet nozzle 13 ... Resistor 14 ... Resistor (division) 15 ... Heat transfer tube support device 16 ... Baffle plate 17 ... Dummy tube 18 ... Flow-ho
Le 19: Feed water inlet tube sheet 20: Steam outlet tube sheet

Claims (2)

(57) [Claims] 1. A helical structure in which a plurality of heat transfer tubes through which a medium to be heated flows are formed in a spiral layer having a constant diameter, and a plurality of other heat transfer tubes are wound outside or inside the spiral layer. A spiral heat transfer tube group whose layers are concentrically combined,
A header to which the ends of the heat transfer tube group are connected, a cylindrical inner tube installed concentrically at the spiral center of the spiral heat transfer tube group, and a concentrically installed outside the heat transfer tube group. In a steam generator comprising an outer cylinder, and a body including the inner cylinder, the heat transfer tube, and the outer tube, a body surrounded by the spiral layers adjacent to each other in one section or a plurality of sections in a direction perpendicular to the axis of the heat transfer tube group. A steam generator, wherein a resistor is provided in the tube bundle axial direction in parallel with the spiral layer for each side flow path. 2. The steam generator according to claim 1, wherein the adjacent spiral layers are adjacent to each other in each body-side fluid flow path region constituted by the adjacent spiral heat transfer tubes. A steam generator characterized in that a rod-shaped resistor having an intermediate curvature of the above and having the same inclination angle as the spiral heat transfer tube is installed in parallel with the spiral layer.