US2420655A - Fluid circulating heat exchanger - Google Patents

Description

L. H. COYKENDALL ETAL FLUID CIRCULATING HEAT EXCHANGER May 20, 1947.

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INVENTORJ Cbg [go/2H. kendal/ QM WP/l .Eawana A TTORNE Y May 20, 1947.

1.. H. COYKENDALL. ET AL 2,420,655

FLUID CIRCULATINQ HEAT EXCHANGER Filed Jan. 15, 1943 5 Sheets-Sheet 2 a d H i g m & M Y m9 w n W, w? m a I M .P Wu? mco H A N H m H .QM QW MW n Y Y B y 20, 1947. 1.. H. COYKENDALL ETAL 2,420,655

FLUID CIRCULATING HEAT EXCHANGER Filed Jan. 15, 1943 5 Sheets-Sheet 3 'INVENTORS 4 0/2 H. Coykenda/l B VVil/Hfiowand v I ATTORNEY M y 0, 1947. L. H. COYKENDALL ETAL 2,420,655

FLUID CIRCULATING' HEAT EXCHANGER Filed Jan. 15, 1943 5 Sheets-Sheet 4 leena'a/l INVENTORS L eon H C BY 21 Will H. Ron and A TTORNE Y Patented May 20, 1947 UNITED STATES PATENT ()FFICE FLUID CIRCULATING HEAT EXCHANGER Application January 15, 1943, Serial No. 472,434

6 Claims. 1

lhis invention relates to vapor generators and it is particularly concerned with the attainment of uniformly good steam qualities from a vapor generator eiiiciently operating at high capacities.

In installations of high capacity steam boiler or vapor generators for the higher pressures it is quite often customary to provide a small number of relatively large diameter water or liquid downcomers from the upper steam and water separating drum to a water supply chamber for the heat absorbing tubes at the lower part of the unit, in order to reduce the frictional resistance to downcomer flow to a minimum.

At the same time it is advantageous to directly connect such downcomers to the water space of the steam and water drum at positions adjacent the drum ends where they can be easily protected from the heat of the furnace gases.

With the discharge of the steam and water from the steam generating tubes through a plurality of connections distributed at spaced positions along the steam and water drum, the separated water must flow longitudinally of the drum in its movement to the downcomer inlets. When the diameter of the drum is relatively small and/or when the longitudinal water flow area is reduced by obstructions, a small lowering ofw the operating water level results in a comparatively great change in the longitudinal water flow area. It has been found that when the level is modified as above explained that there is a tendency for the water level at the entrance of the large downcomers to change rapidly from a low level condition to a high level condition. Such variations in the water level affect the rate of circulation and are therefore not conducive to satisfactory operating conditions.

It is the object of my invention to provide an apparatus for so controlling the longitudinal flow of water from spaced positions along the drum to the entrance of the downcomers that irrespective of drum Water levels, the head at the downcomer inlets will be maintained at a relatively uniform value, so that widely varying rates of circulation will be avoided.

Where the steam generating tubes forming the upfiow part of the circuit are of considerable height, density of the mixture in the tubes is normally the controlling factor in governing the rate of circulation and the rate at which water is withdrawn from the bottom of the large unheated downcomer. It has been found that if the aforementioned height of water in the drum is not maintained within a close range but is allowed to drop, that the amount of water flowing to the inlet of the downcomer may be less than that taken away from the down comer. The result will be a progressive lowering in the level of the water at the downcomer until it reaches such a level that the downcomer water head becomes a factor of suificient effect to reduce the rate of circulation in the circuit. When the low downcomer water level reduces the rate of circulation, then there is a recovery of level for th'e longitudinal flow still continues at substantially the same rate. In fact this rise of water level at the end of the drum may continue to a level above the normal level at the center of the drum after which a reversal ocours with a, repetition of the cycle.

This invention has as one of its primary objects to eliminate, to a large degree, the above described eifects, and to eliminate the consequent carryover of moisture with the steam. In accomplishing these results, the invention provides constructions whereby there is assured a constant supply of substantially solid water to the downcomers.

The invention will be described with reference to a steam generator incorporating a preferred embodiment of the invention and in this embodiment the flow of water is changed from a lengthwise flow of the open channel type to a confined flow within a filled conduit.

The invention will be described with reference to the accompanying drawings and other objects and attributes of th'e invention will appear as the description proceeds.

In the drawings:

Fig. 1 is a vertical section of a steam generator incorporating the invention;

Fig. 2 is a vertical section on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged vertical section of a part Of the steam and water drum of the illustrative steam generator as indicated in Fig. 2. This section is taken on the plane indicated by the section line 3-3 of Fig. 4;

Fig. 4 is a plan section, or a section taken on a horizontal plane through the steam and water drum indicated in Figs. 1, 2, and 3;

Fig. 5 is a vertical section through the steam and water drum, taken on the section line 55 of Fig. 3;

Fig. 6 is a partial vertical section of the downcomer manifold construction taken on the line 6*--6 of Fig. 3;

Fig. '7 is a vertical longitudinal section through 3 a steam and water drum of a modified steam generator provided with the illustrative downcomer manifold construction and having associated therewith means whereby chemicals are introduced into the feed Water to precipitate scale forming constitutents.

Fig. 8 is a horizontal section on the line 88 of the Fig. 7 steam and water drum showing the feed water inlets, the additional chemical feed thereto and the flow of the chemically treated feed water to the main water space of the drum; and

Fig. 9 is a transverse vertical section of the Fig. 7 drum on the plane of the line 99 of Fig. '7. r

Fig. l of the drawings illustrates a steam generator including a steam and Water drum ID connected to a lower drum I2 by upright steam gen: erating tubes. These tubes preferably define the boundaries of a combustion chamber I4, the open pass I6 and a second open pass I8. From'the exit of the latter, furnace gases pass across the screen tubes to a superheater 22 and economizer 24.

Within the drum I0, there is a steam and Water inlet compartment 30 formed between the annularly arranged diaphragm 34 and the inner surface of the drum (see Figs. 5 and 6). This compartment is closed at its ends by such walls as those indicated at 49 in Figs. 3, 4, and 8, and the compartment is closed at its upper portion by such plates or sections as those indicated at 42 and 44 in Fig. 5.

The steam generating tubes communicate directly with the inlet compartment 30, as indicated in Figs. 1 and 5, some of the tubes passing through the wall of the drum at one side and some at the opposite side.

At opposite sides of the drum, and disposed inwardly of the upright parts of the diaphragm 34 are rows of centrifugal steam and water separators as indicated at 50 and 52 in Fig. 5. These separators are supported by the upright parts of the diaphragm 34 and they have substantially tangential inlets communicating directly with the inlet compartment 30. Each separator is of the type indicatedin the Rowand and Fletcher Patent 2,289,970, its tangential inlet leading to a whirl chamber in which the steam and water are separated. Separated steam passes from the top of each whirl chamber, and through a multiple plate separator 5!, to the steam space of the drum, separated water passing through a re stricted opening at the lower end of the separator.

Steam from the separators or cyclones 50 and 52 passes through the scrubber 60 to a plurality of longitudinally spaced steam oiftakes 62, and thence to a point of use.

With reference to the construction shown in Figs. 8 and 9, it will be noted that there are cyclone separators 59' disposed at the end of the drum and beyond the end of the inlet compartment 30. These cyclones 50 have their inlets directly connected with tubes '53 leading from the water outlets of the economizer 24.

It will be seen by reference to the drawings, and particularly Fig. 2. that the separated Water from the cyclones must pass to the end of the drum and thence through the large diameter downcomers 14 and I6 to the lower drum I2, the lower ends of the downcomers I4 and I6 being connected with the latter drum by tubes 8590, and other tubes connecting the downcomers with the headers 92. These headers are the lower side wall headers for the side wall cooling tubes of the furnace I4.

Within the drum I0, and above the lower part of the inlet compartment 30 there are downcomer intake manifolds 8|] and 82. They are, essentially, tubular or tunnel forming constructions using the lower part of the diaphragm 34 as their lower walls and upwardly curved diaphragms for their upper walls. The latter are tapered as indicated in Figs. 2, 3, 4, and 7, and the resulting tapered tubular constructions communicate with the main water space of the drum only through openings such as those indicated at I02 and I03, disposed along the lengths of the manifolds and at low positions in the main water space of the drum.

Each tapered manifold has an outlet I00 directly communicating with and extending into the inlet of a downcomer, as particularly indicated in Fig. 3. The flow area of each manifold progressively increases from a position intermediate the length of the drum to a position near an end of the drum and the cross-sectional flow area of each intake manifold over a downcomer is approximately equal to the area of the downcomer. The flow of the manifold becomes progressively greater and the illustrative construction results in a substantially consistent water velocity condition throughout the manifold length. The water feeds from the drum water space into the manifold through the wide slots I l2iii5 in the side walls of the manifold, the total flow area of these slots in the walls of the manifold being substantially equal to the flow area of the downcomer, or the flow area of the manifold outlet.

Near the outlet end of each manifold, there are fixed guide vanes such as those indicated at I I 0- Ils in Fig. 6, serving to minimize bend losses at the inlets of the downcomers.

Figs. '7, 8, and 9 of the drawings indicate an arrangement of elements associated with the ends of the manifolds to provide for the chemical treatment of the feed water to precipitate scale-forming constituents.

Feed water flows from the Water outlets of the economizer cyclones 58' into a chemical treatment chamber I56 so constructed that the flow of water proceeds from the cyclones 50 past the chemical feed outlet 152 and around the end of an upright wall I54 to a second chemical treatment chamber I556.

The bottom of each of the chambers I56 and I56 is formed by the top of a downcomer manifold and at least parts of the outside walls of these chambers are formed by the sections I60 and I62 of a diaphragm spaced inwardly of the drum walls and secured to an end wall 65 part of which forms a weir over which the chemically treated feed water flows into the main water space of the drum.

The feed water, and particularly raw water make-up, usually contains some scale forming constituents in the form of calcium or magnesium compounds, and chemicals such as sodium phosphate compounds may be fed through the chemical outlet I52 to convert the scale forming compounds to corresponding phosphates which are precipitated as a sludge in the boiler, and, mainly, in the lower parts of the chemical treatment chambers 58 and I55. This deposited sludge may be removed by a continuous or periodic blowdown through blow-down pipes such as those indicated at I it and I72 in the drawings, as par ticularly illustrated in Figs. 7 and 8. These blowdown pipes communicate with the main blowdown I16 connecting with the main water space of the drum at a position intermediate the inner ends of the downcomer inlet compartments 8'6 and 82.

With the construction immediately described above the feed water and treatment chemicals are so introduced that the feed water is retained out of contact with the main body of water within the drum a suflicient length of time to effect a substantial completion of the reactions between the treating chemicals and the scale-forming constituents of the feed water.

What is claimed is:

1. In a steam generator, a steam and water drum in which there is a water level, a plurality of steam generating tubes directly communicating with the drum and distributed throughout its effective length, a plurality of large diameter downcomers leading downwardly from the water space of the drum, means connecting the lower ends of the downcomers to the inlet ends of the steam generator tubes, and an intake manifold for each downcomer, the intake manifolds being disposed within the water space of the drum, each manifold having an outlet directly communicating with the inlet of a downcomer of a similar flow area, each manifold also tapering from its outlet and having a plurality of inlet openings distributed along its length and in direct communication with the water space of the drum, the arrangement of intake manifolds serving to minimize surging of the water within the drum due to endwise flow of the water from the positions of the inlets oi the steam generating tubes toward the downcomers.

2. In a steam generator, a steam and water drum, steam generating tubes communicating with the drum and providing'steam and water inlets therefor, a downcomer leading from the bottom of the drum and communicating with the inlets of the steam generating tubes, downcomer intake means beneath the water level of the drum and including a tubular manifold having its outlet communicating withsaid doun'icomer, said manifold including an upper diaphragm or wall, means forming a feed water inlet adjacent the end of said drum, wall including said diaphragm and combined with said manifold to provide for serie connected feed water treatment chambers separated from the central portion of the drum, the feed water inlet leading to the first of said series connected chambers, and chemical feed means discharging into the first of said chambers on the downflow side of the feed water inlet.

3. In a natural circulation steam generator, a steam and Water drum in which there is a water level, a plurality of steam generating tubes directly communicating with the drum and distributed along its effective length, a plurality of large diameter downcomers leading downwardly from the water space of the drum, means connecting the lower ends of the downcomers to the inlet ends of the steam generator tubes, and an intake manifold for each downcomer disposed within downcomers.

4. In a natural circulation vapor generator, means forming a vapor and liquid chamber in which there is a liquid level, a plurality of vapor generating tubes directly communicating with the chamber and distributed along its effective length, a plurality of large diameter downcomers leading downwardly from the liquid space of said chamber, means connecting the lower ends of the downcomers'to the inlet ends of the vapor generating tubes, and an intake manifold for each downcomer disposed within said chamber, each manifold having an outlet directly communicating with the inlet of a downcomer and having a similar flow area, each manifold also having a plurality of inlet openings distributed along its length and in direct communication with the liquid space of the drum, the sum of the flow areas of the openings in each manifold being at least as great as the flow area of the connected downcomer, the arrangement of intake manifolds serving to minimize surging of the liquid within the drum due to endwise flow of the liquid from the positions of the inlets of the vapor generating tubes toward the downcomers.

5. In a vapor generator, a vapor and liquid chamber, Wall means dividing the chamber into inlet and outlet compartments the latter of which normally has a liquid level therein, vapor generating tubes from which vapor and liquid mixtures are discharged into the inlet compartment, a downcomer adjacent the end of the chamber, means for connecting the lower end of the downcomer with the lower ends of the vapor generating tubes, a plurality of vapor and liquid separators presenting upright whirl chambers within the chamber, means connecting the inlets of the whirl chambers to said inlet chamber to cause whirling movement of the vapor and liquid within the whirl chambers, said whirl chambers having separated liquid outlets at their lower ends and normally disposed below said liquid level, said separators being disposed in a row in the chamber with some of the separators adjacent said downcorner, a tunnel forming structure disposed at the bottom of said outlet chamber beneath the drum water level, the tunnel forming structure having an outlet near one end directly communicatin with the downcomer, and inlet means establishing communication between the liquid space of the outlet chamber and the interior of the tunnel forming structure so that liquid normally flows therefrom to the downcomer in a channel flow.

6. In a steam generator, a steam and Water drum, wall means dividing the drum into inlet and outlet chambers the latter of which normally has a water level therein, steam generating tubes normally discharging steam and water mixtures into the inlet chamber, a large di ameter downcomer adjacent the end, of the drum, means for connecting the lower end of the downcomer wtih the lower ends of the steam generating tubes, a plurality of centrifugal steam and water separators presenting upright whirl chambers within the drum, means connecting the inlets of the whirl chambers to said inlet chamber to cause whirling movement of the steam and water within the whirl chambers, said whirl chambers having separated water outlets at their lower ends and normally disposed below the drum wa- 7 ter level, said separators being disposed in a row longitudinally of the drum with some of the separators adjacent said downcomer, a manifold extending longitudinally of the drum and disposed at the bottom of said outlet chamber beneath the 5 drum water level, the manifold having an outlet near one end directly communicating with the downcomer, and inlet means establishing communication between the water space of the outlet chamber and the interior of the manifold so that the water normally flows therefrom to the downcomer in a channel flow.

LEON H. COYKENDALL.

WILL H. ROWAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,296,426 Coutant Sept. 22, 1942 697,838 Gray Apr. 15, 1902 666,822 Schulz Jan. 29, 1901 1,224,662 Parker May 1, 1917

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