US3833058A

US3833058A - Evaporator

Info

Publication number: US3833058A
Application number: US00349569A
Authority: US
Inventors: J Gulich
Original assignee: Sulzer AG
Current assignee: Sulzer AG
Priority date: 1973-01-09
Filing date: 1973-04-09
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03

Abstract

THE EVAPORATOR IS PROVIDED WITH A DISTRIBUTING CHAMBER WITHIN THE COLD TUBE BRANCHES TO RECEIVE AN INFLOW OF FLUID TO BE EVAPORATED. THE CHAMBER DISTRIBUTES THE FLOW BOTH DOWNWARDLY AND UPWARDLY. THE DOWNWARD PART-FLOW IS DIRECTED TO FLOW AGAINST THE TUBES-BOTTOM AND THEN INTO THE OUTER ANNULAR SPACE BETWEEN THE TANK WALL AND GUIDE WALL. THE FLOW THEN PASSES INTO THE NATURAL CIRCULATION FLOW AND IS DISTRIBUTED ABOUT THE HOT TUBE BRANCHES FROM BELOW. THE UPWARD PART-FLOW IS DIRECTED INTO THE INTERIOR OF THE GUIDE WALL TO MIX WITH THE REST OF THE FLUID.

D R A W I N G

Description

United States Patent Gulich 14 1 Sept. 3,1974

EVAPORATOR Inventor: Johann Gulich, Winterthur,

Switzerland Assignee: Sulzer Brothers LTD., Winterthur,

Switzerland Filed: Apr. 9, 1973 Appl. No.1 349,569

[ 5 7 ABSTRACT The evaporator is provided with a distributing chamber within the cold tube branches to receive an inflow of fluid to be evaporated. The chamber distributes the flow both downwardly and upwardly. The downward part-flow is directed to flow against the tubes-bottom [52] US. Cl. 165/1612, 123/33 and then into the Outer annular Space between the [51] Illlt. Cl F 8b 1 tank wall and guide wall. The flow then passes i h Field Of Search 15/l582163i natural Circulation flow and i distributed about the 165/114 122/3 hot tube branches from below. The upward part-flow is directed into the interior of the guide wall to mix Reference; gjgrENTs with the rest of the fluid.

UNITED STAT S 3,576,179 4/1971 Romanos 122/32 10 5 Drawmgngures 3,706,301 12/1972 Penfield,.|r .7 l65/l6l r A g e 1 l 16 1 20 1 lqqo l 2 l %32 1 1 r l 1 i 1 34 L313 l i 1 3 1 1 1L! V36 5 i K i i L6 l Q l. i 1 I I l I i 38 8" l 1 1 1W i l PAIENIEDSEF 31w SlEUIBfZ 3 3 3 7 5 2 m b 8 nu U 3 3 3 TV llllll I o FIG This invention relates to an evaporator. More particularly, this invention relates to an evaporator for a steam generating plant.

Evaporators have been known to have a vertically oriented pressurized vessel in which a horizontal tubesbottom is disposed to mount a group of U-shaped tubes which for hot tube branches and cold tube branches that extend within the pressurized vessel and conduct a heating medium while an evaporable fluid flows about the tubes. In many instances, conducting means are provided above the tubes-bottom in the region of the hot tube-branches to which the heating medium is conducted in order to distribute the naturally circulating fluid along the section of tubes-bottom equipped with the hot tube-branches and to form upwardlybranched-off fluid flows for passage along the hot tube branches. In addition, these evaporators have also been constructed with a separating wall between the hot tube branches and the cold tube branches (out of which the cooled heating medium is carried away). The separating wall usually extends upwardly and across the entire transverse area of the tubes group. Suitable means are also provided for feeding the fluid into the evaporator.

Such an evaporator is known from Swiss Pat. No. 527,390.1n addition, this evaporator is also provided with guiding means with passages above the tubesbottom section equipped with the cold tube branches in order to distribute the naturally circulating fluid along this section of the tubes-bottom and to form upwardly branched off partial flows. In this way, two naturally circulating fluid flows have been produced in the evaporator and delimited from one another in the region of the separating wall.

However, the heat transfer efficiency of these known evaporators have usually been limited.

Accordingly, it is an object of the invention to increase the heat transfer efficiency of an evaporator.

It is another object of the invention to cool the heating medium passing through an evaporator below the vaporization temperature of the fluid that is to be evaporated before emerging from the cold tube branches.

Briefly, the invention provides an evaporator of the above type with a means for conducting or guiding at least part of the fluid flowing to the evaporator across the cold tube branches as well as with a means for directing at least a part of this fluid sequentially against the tubes-bottom, then past the periphery of the tube group and then, after flowing between the end'edges of the separating wall and the pressure-tank wall, into the space between the conducting or guiding means and the section of the tubes-bottom equipped with the hot tube branches.

The evaporator is thus formed with a preheating zone in the region of the cold tube branches for at least a part of the fluid that is to be evaporated. An intense flow along the tubes-bottom section equipped with the cold tube branches is also produced. Because of the separating wall between the hot and the cold tube branches, the fluid flowing in forced circulation against the tubes-bottom is compelled, after deviation against the pressure-tank wall adjacent to the cold tube branches, to flow onward into the space directly above the section of the tubes-bottom equipped with the hot tube branches. The'preheated fluid is then mixed with the naturally circulating fluid flowing via the guide means. Furthermore, stagnation zones in which any impurities contained in the fluid might otherwise accumulate through evaporation of the fluid are avoided in the region of the heating surfaces.

In one particularly advantageous form of construction, a means is provided for conducting at least a part of the fluid into the space between the cold-and hottubes branches of the group of U-tubes. Because of this, it is possible in a simple way to obtain better utilization of space, which leads to smaller dimensions of the pressurized tank.

In accordance with a further form of construction, the means for conducting or guiding at least a part of the fluid are made so that the fluid, during flow toward the tubes-bottom is guided toward and along the cold tube branches. To this end, displacing elements are used that extend parallel to the cold tube branches and are situated between these branches to leave unobstructed narrow spaces around the tube branches.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a vertical section through the lower end of an'evaporator according to the invention;

FIG. 2 illustrates a view taken on line II-II of FIG.

FIG. 3 illustrates a view taken on line III-III of FIG. 1;

FIG. 4 illustrates a view taken on line IVIV of FIG. 1 and to a greater scale; and

FIG. 5 illustrates a view taken on line V-V of FIG. 1, and to a greater scale.

Referring to FIG. 1, the evaporator of a nuclear reactor plant consists essentially of a pressurized tank 10, a tubes-bottom l and an inflow chamber 4 and an outflow chamber 6 for a heating medium. The heating medium, e.g. water under pressure, before entry into the inflow chamber 4 cools a reactor core as is known and, after giving up heat in the evaporator, flows back to the reactor core. The two chambers 4, 6 are delimited by the tubes-bottom l, by a separating wall 3, and by a spherical bottom 2, to which are connected a connector 5 for the inflow of heating medium, and a connector 7 for the outflow of the heating medium. In addition,

tubes

8,9 are tightly fastened in the tubes-bottom 1. These

tubes

8, 9 are connected, as is known, by bows (not shown) to form a tube grouplZ of U-shaped tubes so as to conduct the heating medium from the inflow chamber 4 to the otuflow chamber 6. As shown, one set of tubes forms hot tube branches 8 connected to the inflow chamber 4 while the other set of tubes forms cold tube branches 9 connected to the outflow chamber, 6. The pressurized tank 10, as is known, merges at the top into a hemisphere. (not shown) which is connected to a connector to remove the steam produced from a flow of water passing around the

tubes

8, 9. The tube groups 12 is surrounded by a tubular guide-wall 16 which defines an annular space with the pressurized tank 10 in which the naturally circulating water to be evaporated flows downward.

A means for guiding the water to be evaporated is positioned above the section of tubes-bottom equipped with the hot tube branches 8. This means is in the form of a flat sheet of metal 45 formed into a surface of a half cone and tightly connected by a curved rim to the lower end of the guide-wall 16. The rectilinear edge of the sheet 45 is, except for a rectangular cut-out opening 46 (FIG. 3), tightly connected to a separating wall 20 which runs upward from the tubes-bottom l and extends over the entire transverse area of the tubes-group 12 (FIG. 2). The metal sheet 45 is provided with passageway openings, through which the tube branches 8 extend with a clearance. In this way, the water flowing downward in the annular space between the pressurized tank 10 and the guide-wall 16 passes over the section of tubes-bottom 1 equipped with the hot tube branches 8, and becomes divided between these branches 8 and the sheet 45 into partial currents.

The separating wall 20 is not situated in the middle of the space between the hot and the

cold tube branches

8, 9 but is shifted toward the cold tube branches 9. Because a portion of the tubes-bottom 1 is thus not equipped with tubes, which results in an unequal distribution of the water at the hot tube branches 8, stumps 47 (shown hatched in FIG. 2) are positioned in the region of this section and fixed on the underside of the metal sheet 45 to simulate the tube branches 8.

A four-cornered box 21 is provided in the lower region of the tubes group 12, between the tube branches 8 on the one hand and the tube branches 9 on the other hand. This four-cornered box 21 extends transversely through the group 12 as far as the guide-wall 16. The two ends of the box 21 are fastened to

connectors

22, 23 respectively, which pass through the wall of the pressurized tank 10, and join

conduits

24, 25, respectively. These

conduits

24, 25 are connected to a common pump 11, which supplies the evaporator with the water that is to be evaporated, e.g. taking the water from a condenser of a steam-turbine unit in which the steam produced by the evaporator is expanded. A number of openings 30 are formed in the separating wall 20 in the region of the four-cornered box 21 and aredistributed along the length of the box 21 to connect the box 21 with a distributing chamber 31. The distributing chamber 31 is delimited above and below by two metal sheets 32, 33 which run from the separating-wall 20 as far as the guide-wall 16, and are tightly welded to these walls. As in the case of the metal sheet 45, passageway openings 33 are provided in the sheets 32, 33 for the passage of the cold tube branches 9 with a clearance so that the water to be evaporated is able to go through these openings out of the chamber 31. The lower sheet 33, delimiting the distributing chamber 31, runs from the separating wall 20 slightly upward whereas the upper sheet 32 runs horizontally. This results in a flow section that decreases outwardly for the distributing chamber 31.

A metal sheet 38 is disposed in parallel to the lower sheet 33 near the tubes-bottom 1, and likewise extends from the separating wall 20 and merges via a curved end into the lower rim of the guide-wall 16. The sheet 38 also has passageway openings like sheet 33. In this way, a space is formed between the sheet 33 and the sheet 38 which houses displacement or supplanting elements 36 (FIG. 4) which extend over the entire height of the space.

Referring to FIG. 4, the elements 36 are of hexagonal cross-section, the sides of the hexagons being alternately straight and concave. The elements 36 are dimensioned so that a narrow interstice 41 is left unobstructed between the concave sides and the tubes 9. Moreover, narrow interstices 42 are formed between the straight sides of adjacent elements 36 for the purpose of taking into account heat-expansion. In order to center the elements 36, two longitudinal beads 40 are provided at the ends of the concave sides respectively, to bear against the tube branches 9.

Referring to FIG. 1, a wall 37 is disposed in parallel to and above the upper delimiting wall 32 of the distributing chamber 31. This wall 37 is connected tightly to the upper end of the separating wall 20 and is welded tightly to the guide-wall 16. Displacement elements 35 are placed in the space formed by the two metal sheets 32, 37. These displacement elements 35 are made and arranged similarly to the elements 36 described above.

Referring to FIG. 2, the guide-wall 16 extends downward as far as the tubes-bottom 1 over a range of 45, in each case measured from the separating wall 20, to form two wall-parts 39. This results in a 90 opening between the two wall-parts 39. As a result, the water which flows through the openings in the metal sheet 38 passes through the opening between the wall-parts 39 into the annular space between the wall-parts 39 and the adjacent pressure-tank wall. Thereafter, the water can flow into the space between the metal sheet 45 and the section of tubes-bottom 1 equipped with the hot tube branches 8 and can become mixed with the naturally-circulating water.

The center of the tubes-bottom 1 is provided with a blind hole 48. As shown in FIG. 5, the bottom of the blind hole 48 communicates with an upwardly-slanting bore 49 to which a conduit 50 is connected. The conduit 50 runs along the tubes-bottom 1 and out of the evaporator (FIG. 2), for the purpose of removing sludge.

In the operation of the evaporator, 90 percent of the total fluid or water to be evaporated is, for example, fed through the

pipes

24 and 25 to the four-corners box 21. The fluid then flows, by way of the openings 30, into the distributing chamber 31. Approximately half of the quantity of fluid, 45 percent that is, then flows, forcibly actuated, through the

gaps

41 and 42 of the tube branches 9 and between the displacement elements 36 downward towards the tubes-bottom 1. After flowing through the passageway openings in the metal sheet 38, the fluid, while intensively washing the section of the tubes-bottom 1 equipped with the cold tube branches 9, flows radially outward to the periphery of the group of cold tube branches 9, and arrives, by way of the 90 opening, between the wall-parts 39 in the annular space between the wall parts 39 and the adjacent wall of the pressurized tank. The fluid then flows in this annular space along the periphery of the tube group and after passing the end edges of the separating wall 20 arrives in the space below the metal sheet 45. The other half of the fluid flowing into the distributing chamber 31 flows between the elements 35 upward in a direction toward the cold tube branches 9. After flowing through the passageway openings in the sheet 37 into the space enclosed by the guide wall 16, the fluid mixes with the remaining fluid that flows, by way of the sheet 45, into the space enclosed by the guide-wall 16. The remaining of the fluid that is to be evaporated is fed through a connector into the annular space between the pressurized tank 10 and the guide-wall 16 in a way known of itself, approximately at the level of the fluid to be evaporated.

The slope of the metal sheet 45 should be made such that the section of the tubes-bottom l equipped with the hot tube branches 8 is washed with sufficient speed as far as the region of the blind hole 48. If a preheating of the fluid that is to be evaporated occurs at the cold tube branches 9 sufficient to bring the fluid up to saturated-steam temperature, then it is possible for so great a formation of steam to occur between the metal sheet 45 and the tubes-bottom 1, that the slope of the sheet 45 may be zero or even negative.

A baffle (not shown) can be provided in the annular space between the pressurized tank 10 and the guidewall 16 adjacent to the cold tube branches 9 to extend 180 about at the height of the section line IVIV in FIG. I. This baffle would prevent the preheated fluid emerging from the metal sheet 38 from flowing upward into the annular space.

What is claimed is:

1. In an evaporator having a pressurized tank, a horizontal tubes bottom extending across said tank, a group of U-shaped tubes mounted in said tubes bottom and including hot tube branches and cold tube branches for conducting a heating medium therethrough, a separating wall between said hot tube branches and said cold tube branches and extending across said group, means for feeding a fluid to be evaporated into said tank, and means above said tube-bottom and between said hot tube branches for distributing a naturally circulating flow of the fluid flowing across said tubes bottom upwardly into a plurality of part flows; first means for guiding at least a part-flow of the fluid fed into said tank across said cold tube branches and second means for directing at least a portion of said part-flow sequentially against said tubes-bottom past the periphery of said group of tubes, and into said means above said tubes-bottom.

2. In an evaporator as set forth in claim 1, said first means being disposed between said hot tube branches and said cold tube branches.

3. In an evaporator as set forth in claim 1, displacement elements extending between said cold tube branches in parallel to define narrow unobstructed spaces therebetween for the flow of fluid therebetween.

4. An evaporator comprising a tank;

a horizontal tubes-bottom extending across said tank;

a group of U-shaped tubes mounted in said tubesbottom to define hot tube branches and cold tube branches;

a separating wall between said hot tube branches and said cold tube branches, said wall extending across said group of tubes;

a guide wall surrounding said group of Ushaped tubes and spaced from said tank to define an annular space therewith;

a first means for guiding a delivered flow of fluid across said cold tube branches;

second means connected to said first means for directing at least a portion of the delivered flow downwardly along said cold tube branches against said tubes-bottom and outwardly into said annular space; and

a third means between said guide wall and said separating wall and above said tubes-bottom for receiving and distributing a flow of fluid from said annular space into a plurality of part-flows of fluid upwardly along said hot tube branches within said guide wall.

5. An evaporator as set forth in claim 4 wherein said first means includes a box between said hot tube branches and said cold tube branches for receiving an inflow of fluid and a pair of sheets extending from said box across said cold tube branches to define a distributing chamber therebetween for receiving fluid from said box.

6. An evaporator as set forth in claim 5 wherein said second means includes a sheet extending from said separating wall to said guide wall across said cold tube branches and between said distributing chamber and said tubes-bottom, said sheet forming a clearance with each cold tube branch for directing a part flow of fluid against said tubes-bottom.

7. An evaporator as set forth in claim 6 wherein said third means is a sheet forming a clearance with each hot tube branch.

8. An evaporator as set forth in claim 6 which further comprises displacement elements between said cold tube branches and defining narrow spaces therewith for passage of fluid therebetween.

9. An evaporator as set forth in claim 4 wherein said second means includes a sheet extending from said separating wall to said guide across said cold tube branches above said tubes bottom, said sheet forming a clearance with each cold tube branch for directing a part flow of fluid against said tubes-bottom.

10. An evaporator as set forth in claim 4 further comprising fourth means connected to said first means for directing another portion of the delivered flow upwardly along said cold tube branches to mix with the part-flows of fluid passing through said third means within said guide wall.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 33, 5 Dated Sep em er 3, 197

Inventor(s) Johann Gulich It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Insert the priorityparticulars to read as follows:

- --'January 9, 1973 Switzerland 252/73.

Column 2,flin e 51, "otuflow'f should be --outflow--.

Signed and sealed this 3rd day of Deeeraber 1974.

' (SEAL) Attest:

IIcCOY M. GIBSON JR. C IIARSHALL DANN Attesting Officer. Commissioner of Patents FORM PO-IOSO uo-es) 4 USCOMWDC 6 5. U.S. GOVERNMENT PRINTING OFFICE: I", O-BiE-J Sl.