JPS631517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tubular heat exchanger, and particularly to a heat exchanger suitable for use in structural discontinuities, etc., which are subject to severe thermal shock during thermal transients.

A conventional heat exchanger will be explained with reference to FIG.

The outer shell 1 has a primary sodium inlet nozzle 2 and a primary sodium outlet nozzle 6.

The secondary side upper end plate 3 is integrated with the upper tube plate 4,
A secondary side upper plenum 5 is formed inside, and 2
It has a secondary sodium outlet nozzle 7.

The heat exchanger tube bundle 9 has an upper end connected to the upper tube plate 4 and a lower end connected to the lower tube plate 8, and includes a heat shield plate 11 near each tube plate.

Further, an external shroud 10 is installed surrounding the outside of the heat exchanger tube bundle 9 and having an inlet window 12 at the upper part and an outlet window 13 at the lower part.

The secondary sodium inlet pipe 15 passes through the secondary upper end plate 3, the upper tube plate 4, and the lower tube plate 8 and has a lower end opening in the secondary lower plenum 14.

The primary high-temperature sodium is introduced into the outer shell 1 through the primary sodium inlet nozzle 2, flows into the outer shroud 10 through an inlet window 12 provided in the outer shroud 10, and rises within the heat exchanger tube bundle 9. It descends while exchanging heat with the secondary sodium, passes through the outlet window 13 provided at the bottom of the external shroud 10, and flows out of the equipment from the primary sodium outlet nozzle 6.

On the other hand, the secondary side low-temperature sodium flows into the equipment from the secondary sodium inlet pipe 15, reaches the secondary side lower plenum 14, turns around, and flows into the heat exchanger tube provided in the lower tube plate 8. It rises while exchanging heat with sodium, reaches the secondary side upper plenum 5, and flows out of the equipment from the secondary sodium outlet nozzle 7.

An example of a conventional structure for fluid flow is shown in FIG. In the figure, the baffle plate 16 is attached close to the external shroud 10 that encloses a plurality of heat exchanger tube bundles 9, and has a large number of through holes to adjust the circumferential flow distribution of the primary high temperature sodium fluid. It is designed to be even.

Further, an inlet window 12 is provided in the upper part of the external shroud 10 in the circumferential direction, and serves to guide the fluid into the heat exchanger tube bundle 9.

A primary sodium inlet nozzle 2 is provided in the outer shell 1 for introducing hot sodium fluid into the equipment. The primary sodium inlet nozzle 2 is installed at a position slightly above the center of the heat exchanger tube bundle 9.

Further, above the inlet window 12, a structural discontinuity is formed in which a shroud is connected to the upper tube plate 4 where the heat exchanger tube bundle 9 is assembled.

Such a structure causes the following drawbacks.

(1) Although there is fluidity from the primary sodium inlet nozzle to the inlet window, there is no fluidity in the area surrounded by the upper tube plate and outer shell, resulting in a stagnant sodium layer.

(2) From item 1 above, when a thermal shock occurs due to a sudden temperature change, especially in the structural discontinuity between the upper tube plate and the shroud, the fluid has no fluidity and heat tracking is not accompanied. Significant thermal stress is generated.

(3) It can be said that vibration and pressure loss due to fluid flow are extremely large.

(4) It is impossible to obtain the optimum flow rate distribution of the fluid.

An object of the present invention is to form a stagnant primary fluid layer in a portion surrounded by an upper tube plate and an outer body by installing a longitudinal cylindrical weir connected to an external shroud. The purpose of the present invention is to provide a structure for providing a suitable flow rate to a flow rate and obtaining temporal thermal tracking during thermal transients.

The present invention installs a heat shield plate below the upper tube plate,
A heat exchanger that has a primary fluid inlet window into the external shroud at a position below the heat shield plate, and an outer shell that sandwiches a vertical flow path for the primary fluid around the outer periphery of the primary fluid inlet window. A rectifying plate is provided in the vertical flow path above the primary fluid inlet nozzle to the outer shell and below the primary fluid inlet window, and a rectifying plate is provided in the vertical flow path above the rectifying plate. A heat exchanger comprising a cylindrical weir extending above the height of the primary fluid inlet window, the lower end of which is closed between the external shrouds, and the upper end of which is open. According to the exchanger, the primary fluid flows upward along the weir through the flow path constricted by the weir, then bends at the upper end of the weir, descends, and enters the inlet window, and the constriction increases the effective flow velocity. The upflow destroys the upper stagnant layer and is guided to the entrance window.

An embodiment of the present invention will be described based on FIG.
In the figure, a large number of heat exchanger tube bundles 9 are assembled, and is formed of an upper tube plate 4 serving as a boundary for primary and secondary sodium, an outer shroud 10 that protects and encloses the heat exchanger tube bundle 9, and an outer shell 1. ing.
A shroud is provided as a connection between the upper tube plate 4 and the outer shell 1, and the structure requires an upward slope as shown in the figure.

The inlet windows 12 have through-holes opened at several locations in the circumferential direction of the external shroud 10 in the vicinity of the upper tube plate 4, providing a uniform flow rate distribution in the circumferential direction.

This entrance window 12 is located directly below the upper tube plate 4.
It is installed considerably below the upper tube plate 4 so as to avoid the heat shield plate 11 which is installed in multiple layers to alleviate thermal shock to the upper tube plate 4.

Furthermore, a longitudinally cylindrical weir 17 is incorporated in the external shroud 10 so as to enclose the inlet window 12, and is structured to prevent the high temperature sodium flowing in from the primary sodium inlet nozzle 2 from entering directly. There is. Furthermore, the longitudinal cylindrical weir 17 is characterized in that it extends beyond the inlet window 12 to a structural discontinuity between the upper tube plate 4 and the shroud.

According to the heat exchanger having such a structure, the primary sodium, which is the primary fluid that enters the outer shell 2 from the inlet nozzle 2, has a flow rate as uniform as possible around the outer circumference of the outer shroud 10 when passing through the porous rectifying plate 16. distributed. Thereafter, the primary sodium ascends through the vertical flow path, which is narrowed to approximately half its width by the weir 17, as indicated by the white arrow. At this time, the flow rate increases by the amount of restriction, and all the primary sodium is
7, so the force of the flow is large.
This flow of large force is diverted at the upper end of the weir 17, where the upper stagnant primary sodium layer is destroyed, guided downward to the entrance window 12 side, and enters the external shroud 10 where it is subjected to heat exchange action. . In addition, by changing the cylindrical diameter of the weir 17 to narrow or widen the ascending flow path for primary sodium, the flow force of the ascending flow that hits the stagnant primary sodium in the upper part can be freely changed.

In this way, the entire flow rate of primary sodium is utilized and its flow force is used to destroy the stagnant layer. According to this method of use, even if the primary sodium flow rate decreases, the destructive action can be maintained as much as possible.

According to one embodiment of the present invention, the following effects are achieved.

(1) By adjusting the diameter of the longitudinal cylindrical weir in the radial direction, it is possible to freely change the fluid flow velocity.

(2) According to the above-mentioned item 1, effective flow is provided to the sodium layer of the stagnant formed in the area surrounded by the upper tube plate and the outer shell, and thermal tracking that can cope with thermal shock due to sudden temperature changes is obtained. be able to.

(3) Since the longitudinally cylindrical weir is installed so as to enclose the entrance window, it has a heat shielding effect due to the high temperature fluid.

(4) The weir 17 is thin-walled in the longitudinal direction and has a cylindrical shape, and it has been experimentally proven that the pressure loss is low because there is flow inside and outside of the cylindrical weir.

The present invention has the following effects.

In a heat exchanger equipped with a heat shield plate directly below the upper tube plate, effective heat tracking at structural discontinuities is provided by efficiently suppressing the generation of a stagnant layer using the entire flow force of the primary fluid. be able to.

Furthermore, the present invention is not limited to intermediate heat exchangers;
It can be applied to steam generators of fast reactors, steam generators of pressurized water reactors, heat exchangers in thermal power plants, etc.

[Brief explanation of the drawing]

FIG. 1 is an overall diagram of a heat exchanger, FIG. 2 is a diagram of a conventionally implemented structure, and FIG. 3 is a diagram of a preferred weir structure in the present invention. 1... Outer shell, 2... Primary sodium inlet nozzle, 4
... Upper tube plate, 9 ... Heat exchanger tube bundle, 10 ... External shroud, 11 ... Heat shielding plate, 12 ... Inlet window, 16 ... Straightening plate, 17 ... Weir.

Claims (1)

[Claims] 1. A heat shield plate is installed below the upper tube plate, and a primary fluid inlet window into the external shroud is provided below the heat shield plate. In a heat exchanger comprising an outer shell across a directional flow path, a rectifying plate is provided in the vertical flow path above the primary fluid inlet nozzle to the outer shell and below the primary fluid inlet window, A cylindrical weir is provided in the vertical flow path above the rectifying plate, and extends above the height of the primary fluid inlet window, and has a lower end closed between the external shrouds and an upper end open. A heat exchanger characterized by: