JP3407722B2 - Combination heat exchanger - 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 for exchanging heat between two different fluids which must avoid contact with each other, and more particularly to a liquid metal cooled fast breeder reactor for exchanging heat between water and liquid sodium. Of steam generators.

[0002]

2. Description of the Related Art In a steam generator for a liquid metal cooled fast breeder reactor using sodium, when a single heat transfer tube is used, sodium and water immediately contact with each other when the heat transfer tube is damaged to cause a sodium water reaction. Therefore, there is a demand for a highly reliable heat exchanger that does not immediately lead to malfunction even if damage occurs.

For this reason, conventionally, as a steam generator for a liquid metal cooling fast breeder reactor, a double-tube steam generator which is divided into an inner tube and an outer tube and is independent, a sodium side heat transfer tube and a water / steam side heat transfer tube. Separated tube steam generators have been considered. The double heat transfer tubes of the double tube heat exchanger include a close contact double tube, a double tube with a braided wire, and a double tube with a gap. For example, Japanese Patent Application Laid-Open No. 6-323777 discloses a double tube heat exchanger with a braided wire. In all of these, the gap between the inner tube and the outer tube is about several microns to several millimeters, and there is a possibility that the inner tube and the outer tube may be damaged at the same time when a large force is applied. If the distance between the inner pipe and the outer pipe is increased to reduce the possibility of simultaneous breakage, the thermal resistance of the gap between the inner and outer pipes of the double pipe increases and the heat transfer performance deteriorates.

On the other hand, in the separated steam generator, the sodium heat transfer tube and the water / steam heat transfer tube are positionally independent,
There is less chance that both heat transfer tubes will break at the same time due to a single cause. However, the separation tube type steam generator is one in which a metal block or a liquid metal having excellent thermal conductivity such as bismuth, tin, or indium is arranged between heat transfer tubes that pass two fluids to perform heat exchange by heat conduction. Therefore, the amount of intermediate heat medium arranged in the heat exchanger becomes huge, and
There was an economic problem because the structure was complex and large.

[0005]

Therefore, the problem to be solved by the present invention is to reduce the possibility of mixing two different fluids which must avoid contact with each other even if the heat transfer tube is broken. It is intended to provide a small and lightweight heat exchanger, and particularly to provide a heat exchanger having a high degree of freedom of design suitable for a steam generator of a liquid metal cooled fast breeder reactor.

[0006]

A combination type heat exchanger of the present invention for solving the above-mentioned problems is provided with a large number of concentric layers of helical coil heat transfer tubes in a body, and a large number of layers between helical coil heat transfer tube layers. By providing a layer in which the straight pipe heat transfer pipe is arranged, the first fluid is passed through the helical coil heat transfer pipe, the second fluid is passed through the straight pipe heat transfer pipe, and an intermediate portion is provided between the straight pipe heat transfer pipe and the helical coil heat transfer pipe. It is characterized in that the heat medium is filled so that heat exchange between the first fluid and the second fluid is carried out through natural convection of the intermediate heat medium.

In the combined heat exchanger of the present invention, since the helical coil heat transfer tube for passing the first fluid and the straight tube heat transfer tube for passing the second fluid are separated and independent from each other, they can be simultaneously damaged by a single cause. Therefore, the possibility that a contact reaction between the first fluid and the second fluid will occur is reduced. Further, since the natural convection of the intermediate heat medium having high thermal conductivity is used, the heat transfer efficiency is higher than that of a simple double tube. Further, the number of straight tube heat transfer tubes is not restricted by the number of helical coil heat transfer tubes, and the tube length of the helical coil heat transfer tubes is not restricted by the tube length of the straight tube heat transfer tubes. Therefore,
Since the first fluid and the second fluid can be passed through the heat transfer tubes having different shapes that can be designed independently, the degree of freedom in design is increased, and the two fluids can be configured based on the optimum conditions. As described above, according to the present invention, not only the design of the heat exchanger becomes extremely easy, but also the quantity of the device can be reduced.

When the combination heat exchanger is installed vertically, an inner cylinder is provided at the axial position of the combination heat exchanger, and the inner cylinder is radially arranged with the inner cylinder at predetermined intervals. It is preferable to provide a ladder that hangs from a plurality of beams provided. A ladder having a through hole provided substantially horizontally is fixed to the beam, and the helical coil heat transfer tube is supported by the through hole. Further, a baffle plate having a plurality of vertically provided through holes is fixed between adjacent ladders, and the straight tube heat transfer tube is supported by the vertical through holes. By adopting such a configuration, two types of heat transfer tubes having different shapes can be easily housed and fixed in one heat exchanger. Further, in this configuration, since the heat transfer tube for the first fluid and the heat transfer tube for the second fluid have different support methods, the simultaneous breakage phenomenon is further unlikely to occur.

Further, the vertically arranged heat exchanger preferably includes a support structure at the upper end of the inner cylinder. This support structure is composed of a plurality of support beams that are radially provided with the inner cylinder as an axis and whose ends are fixed to the outer wall of the combined heat exchanger.
The ends of the helical coil heat transfer tubes are assembled on a support beam and joined to a nozzle provided on the side of the combined heat exchanger,
The ends of the straight pipe heat transfer tubes between the support beams are joined to the nozzles provided at the ends of the combined heat exchanger. By doing so, it is possible to prevent confusion due to the presence of a large number of heat transfer tubes at the end of the heat exchanger, and to supply and discharge the fluids passing through the two kinds of heat transfer tubes in an organized manner. Also, it enables economical manufacturing by simplifying construction.

The heat exchanger of the present invention can be used for general industry as a heat exchanger for handling two liquids which may cause an accident when the heating side fluid and the cooling side fluid are mixed.
In particular, it exerts a great effect when applied to heat exchange between water and sodium metal, which is often used in a steam generator of a liquid metal cooled fast breeder reactor. In the steam generator of the liquid metal cooled fast breeder reactor, the sodium flow rate is about 10 times the water / steam flow rate, and the allowable pressure loss of sodium is about 1/10 or less of the water / steam flow rate. Therefore, it is preferable that the liquid sodium is passed through the vertical tube having a short tube length, and the water / steam is passed through the helical coil type heat transfer tube. As the intermediate heat medium, it is possible to use lead, bismuth, tin, indium, or a mixture thereof, which does not easily react with water or sodium and has high thermal conductivity.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on embodiments with reference to the drawings. In this embodiment, the heat exchanger of the present invention is applied to a steam generator of a liquid metal cooled fast breeder reactor. 1 is a partial cutaway view of the steam generator of the present embodiment, FIG. 2 is a sectional view of the steam generator shown in FIG. 1 rotated by 45 degrees, and FIG. 3 is a plan view showing the top of the steam generator. FIG. 4 is a horizontal cross-sectional view showing a state cut along the plane AA of FIG.

The steam generator of the present embodiment is a vertical water / sodium heat exchanger in which a helical coil heat transfer tube and a straight tube heat transfer tube are combined.
A large number of layers each of which is concentrically provided, and a layer in which a large number of straight tube heat transfer tubes 3 are arranged in the axial direction is provided between the respective layers of the helical coil heat transfer tube layers. Water and steam are passed through the helical coil heat transfer tube 2, liquid sodium is passed through the straight tube heat transfer tube 3, and liquid phase lead bismuth is filled as the intermediate heat medium 4 in the heat exchange region to allow natural convection of the intermediate heat medium. To exchange heat between liquid sodium and water / steam.

The helical coil heat transfer tubes 2 are arranged in one layer by stacking spirally wound heat transfer tubes with the same curvature in parallel in an appropriate number of axial directions. The plurality of helical coil heat transfer tube layers have different winding diameters, but if the heat transfer tubes have the same inclination angle, the heat transfer tubes have the same length and can be treated as equivalent heat transfer tubes. The straight tube heat transfer tube 3 is formed by arranging straight tubes extending in the axial direction of the steam generator in a row along the circumference to form a cylindrical layer. The layers of the helical coil heat transfer tube 2 and the layers of the straight tube heat transfer tube 3 are alternately arranged adjacent to each other in the radial direction.

The steam generator is provided with an inner cylinder 5 at an axial position, and a plurality of ladders 6 for supporting the helical coil heat transfer tubes 2 are mounted in the circumferential direction. Through holes 7 are provided in the ladder 6 at positions intersecting with the layers of the helical coil heat transfer tubes 2 side by side in the axial direction of the steam generator to pass the helical coil heat transfer tubes 2. Since the helical coil heat transfer tube 2 is easily bent in the vertical direction, the helical coil heat transfer tube 2 is fixed to the ladder 6 at an appropriate interval, for example, every other one, but it is merely supported at other positions to relieve the thermal stress acting on the heat transfer tube. ing. FIG. 4 shows an example in which four ladders 6 are provided,
The appropriate ladder number varies depending on the conditions.

Fan-shaped baffle plates 8 are mounted between the ladders 6 at appropriate intervals in the axial direction. The baffle plate 8 is arranged at a position corresponding to the layer of the straight tube heat transfer tube 3, and holds the straight tube heat transfer tube 3 so that the position of the straight tube heat transfer tube 3 does not change by a through hole 9 opened in the axial direction of the steam generator. The through hole 9 of the baffle plate 8 has a drum-shaped cross section so that the tube wall is less likely to be damaged even when the heat transfer tube vibrates or is displaced. Straight tube heat transfer tube 3
Since the support in the gravitational direction is performed by the tube plates near both ends of the steam generator, it is not necessary to fix the straight tube heat transfer tube 3 to the baffle plate 8.

FIG. 5 is a perspective view schematically showing the assembled state of the ladder 6 and the baffle plate 8, and FIG. 6 is a partially enlarged sectional view thereof. The ladder 6 is provided in a heat exchange area where the heat transfer tube 2 is in the shape of a helical coil, is assembled from a connectable block in units of one layer of the helical coil heat transfer tube 2, and is attached to the inner cylinder 5. . The baffle plate 8 is provided in a fan-shaped portion sandwiched between the ladders 6 and fixed to the ladders 6 with bolts 10. The bolt 10 can also serve to fix the blocks of the ladder 6 to each other.
The inner cylinder 5 includes beams 11 and 1 fixed to the upper and lower sides of the body 1, respectively.
2 supports the weight of the heat transfer tube. In addition,
Since the heat transfer tube is immersed in lead bismuth during operation, a large buoyancy is generated, so that the beams 11 and 12 can withstand both gravity and buoyancy.

The straight tube heat transfer tube 3 is guided by a baffle plate 8 and corresponds to the tube plate 14 of the sodium inlet nozzle 13 provided in each region sandwiched by the ladder 6 at the top of the steam generator and the sodium inlet nozzle 13. It is supported between the tube sheets 16 provided on the bottom sodium outlet nozzles 15.
The thermal stress can be absorbed by the curved tube portion 17 provided at the bottom. The helical coil heat transfer tube 2 is a tube plate 19 of the water supply nozzle 18 provided on the lower side surface of the steam generator.
It is fixed by, and rises from the vicinity of the lower beam 12 to the helical portion while avoiding the straight pipe heat transfer tube 3, and is connected to the helical portion.
The helical coil heat transfer tube 2 goes around the helical portion and avoids the rising of the straight tube heat transfer tube 3 at its upper end,
Standing up beside the upper beam 11 that supports the space, the space formed in the upper beam of the upper beam 11 and the upper shroud of the steam generator is used to collect the tube sheet collected in the steam outlet nozzle 20 provided on the upper side surface of the steam generator. It is fixed at 21. The steam generator has a skirt 2
It is fixed to the support structure by 2.

When the steam generator is operated, water is supplied from the water supply inlet nozzle 18 of the water supply inlet header 22 to the helical coil heat transfer tube 2 and receives the heat of liquid sodium through the natural convection of lead bismuth 4 to generate steam. And steam header 2
After being collected in 3, the steam is discharged from the steam outlet nozzle 20 to a steam turbine generator or the like (not shown). On the other hand, liquid sodium, which is a coolant for the liquid metal cooling fast breeder reactor, is supplied from the sodium nozzle 13 of the sodium inlet header 24 to the straight pipe heat transfer pipe 3
And sodium outlet header 2 provided at the bottom
Collected in 5 and returned to the liquid metal cooling fast breeder reactor (not shown) from the sodium outlet 1.

In the liquid metal cooled fast breeder reactor, the flow rate of sodium is about 10 times the flow rate of water / steam, and the pressure loss observed in sodium in the steam generator is about 1/10 of that of water / steam. Below that. In conventional helical coil steam generators, sodium and water / steam heat transfer tubes located in the same coil layer were alternately arranged adjacent to each other.In such a configuration, sodium heat transfer tubes and water / steam heat transfer tubes are arranged. Since they have the same length, the sodium heat transfer tube becomes excessively long, and the tube diameter had to be increased in order to suppress the pressure loss. Then, the flow velocity of sodium flowing in the pipe is lowered and the heat transfer performance is deteriorated, so that the heat transfer area has to be increased and the amount of the material as the heat exchanger is increased, which causes a cost increase. In addition, in a straight-tube steam generator, since the pipe length is limited, the pressure loss of the water / steam heat transfer pipe is small and the flow velocity in the pipe is small, so the heat transfer performance deteriorates. As a result, the quantity of the exchanger is increased and the cost is increased.

In the present invention, sodium is passed through the straight tube heat transfer tube and water and steam are passed through the helical coil heat transfer tube, so that the most suitable dimensions can be selected independently. In a fast breeder reactor, the flow rate of sodium is large, but the pressure loss must be small, but assuming that the length of the heat exchanger is fixed, the diameter and number of straight heat transfer tubes must be set to an appropriate pressure loss and flow rate inside the tube. By selecting so as to obtain, the heat transfer area can be reduced and the quantity and cost can be reduced. Also, for water and steam, since the helical coil heat transfer tube is used, it is possible to reduce the quantity and cost by appropriately adjusting the heat transfer tube length and in-tube flow rate to select heat transfer performance optimally. .

Further, in the helical coil heat exchanger,
Since the sodium heat transfer tubes and the water / steam heat transfer tubes were alternately arranged in one heat transfer tube layer, the convection of the intermediate heat medium was difficult to grow because the high temperature region and the low temperature region appeared in the vertical fine cycle. It was However, in the combined heat exchanger of the present invention, two types of heat mediums of sodium and water / steam are
Since only the heat transfer tubes through which the same heat medium passes are formed as a cylindrical layer, the upflow and downflow of the intermediate heat medium grow sufficiently, so the heat medium in the tank causes large natural convection. It has good heat transfer characteristics.

For example, in a liquid metal cooled fast breeder reactor
And superheat the water with the heat of 1000 MW of sodium
When using a helical coil type heat exchanger,
730 heat transfer tubes for sodium, water and steam
Diameter 7.2 m, height 23.2 m, weight 860 tons, NAT
The total heat transfer area of rumium, water and steam is 14370m.²Tona
In a straight tube evaporator, there are 4843 heat transfer tubes each
Is 4.2m, height is 33.5m, weight is 800 tons, Natri
Total heat transfer area of um and water / steam is 12570m ²Tona
It

Under the same conditions, in the combination heat exchanger of the present invention, 7710 straight sodium heat transfer tubes for water,
527 helical coil heat transfer tubes for steam, diameter 5.7m,
The height is 25 m, the quantity is 720 tons, and the total heat transfer area of sodium and water / steam is 11330 m ² . As described above, according to the present invention, since the design can be performed based on the optimum conditions, respectively, the heat transfer area becomes extremely small and the amount of material is reduced. Moreover, the size of the heat exchanger is reduced, and the cost is reduced.

In the above embodiment, for convenience, the helical coil heat transfer tube and the straight tube heat transfer tube each have four layers, and the case where the number of ladders is four has been described. Needless to say, it changes depending on.
The position and the number of nozzles can be determined independently of the position of the ladder. In particular, since the water / steam heat transfer tube can be easily routed within the shroud, the nozzle position can be determined more freely. Further, although lead bismuth is adopted as the intermediate heat medium, it is needless to say that an optimum medium such as antimony / bismuth can be selected depending on the heat exchange conditions. Furthermore, in the present embodiment, the heat exchanger of the present invention was used for water-sodium heat exchange, but in addition to this, a great effect is brought about when two heat mediums for heat exchange of the present invention bring an inconvenient result. It goes without saying that there is

[0025]

As explained above, in the heat exchanger of the present invention, since the straight pipe heat transfer tube and the helical coil heat transfer tube are applied to different media, there is a possibility that both media will come into contact with each other even if there is any inconvenience. Few. In addition, since optimum conditions can be achieved independently for both media, more flexible design can be achieved, and heat transfer area, quantity, cost, etc. of the heat exchanger and steam generator can be optimized. it can.

[Brief description of drawings]

FIG. 1 is a partial cutaway view of a steam generator of a liquid metal cooled fast breeder reactor to which a heat exchanger of the present invention is applied.

FIG. 2 is a cross-sectional view of the heat exchanger of this embodiment.

FIG. 3 is a plan view showing the top of the heat exchanger of this embodiment.

FIG. 4 is a horizontal sectional view taken along the line AA of FIG.

FIG. 5 is a perspective view schematically showing an assembled state of a ladder and a baffle plate used in this embodiment.

FIG. 6 is an enlarged cross-sectional view of an assembled portion of the ladder and the baffle plate of this embodiment.

[Explanation of symbols]

1 torso 2 Helical coil heat transfer tube 3 straight tube heat transfer tube 4 Intermediate heat medium 5 inner cylinder 6 ladder 7 through holes 8 baffle board 9 through holes 10 volts 11 Upper beam 12 Lower beam 13 Sodium inlet nozzle 14 tube sheet 15 Sodium outlet nozzle 16 tube sheet 17 curved pipe 18 Water inlet nozzle 19 tube sheet 20 Steam outlet nozzle 21 tube sheet 22 Water inlet header 23 Steam header 24 sodium inlet header 25 sodium outlet header

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G21C 1/02 F22B 1/06 F28F 11/00 G21C 15/02 G21D 1/00

Claims (4)

(57) [Claims] 1. A heat exchange in which a large number of layers of helical coil heat transfer tubes are concentrically provided in the body, and a layer in which a large number of straight tube heat transfer tubes are axially arranged is provided for each layer of the helical coil heat transfer tube layers. A first fluid is passed through the helical coil heat transfer tube, a second fluid is passed through the straight tube heat transfer tube, and an intermediate heat medium is filled between the straight tube heat transfer tube and the helical coil heat transfer tube. Then, the first convection is conducted through natural convection of the intermediate heat medium.
A heat exchanger for exchanging heat between the fluid and the second fluid. 2. The combination heat exchanger is installed vertically, an inner cylinder is provided at an axial position of the combination heat exchanger, and a plurality of ladders are radially provided with the inner cylinder as an axis, and the ladder is attached to the ladder. Is a large number of horizontal through-holes, which are laid horizontally in the axial direction, are continuously provided at positions of each layer of the helical coil heat-transfer tube layer, the horizontal through-holes support the helical coil heat-transfer tubes, and at predetermined positions in the axial direction. Fixing a baffle plate having a plurality of vertical through holes vertically provided in a portion of each layer of the straight tube heat transfer tube layer sandwiched between the ladders, and supporting the straight tube heat transfer tube by the vertical through holes. The combined heat exchanger according to claim 1, wherein: 3. A support structure is provided on an upper end portion of the inner cylinder,
The support structure comprises a plurality of support beams which are radially provided with the inner cylinder as an axis and whose end portions are fixed to the outer wall of the combination heat exchanger, and the straight pipe heat transfer tube between the support beams. The end of the helical heat transfer tube is joined to the nozzle provided at the end of the combined heat exchanger, and the end of the helical coil heat transfer tube is gathered near the support beam and provided at the side of the combined heat exchanger. The combined heat exchanger according to claim 2, wherein the combined heat exchanger is joined to the nozzle. 4. The combined heat exchanger according to claim 1, wherein the first fluid is water or steam and the second fluid is liquid sodium.