US2858809A - Superheater - Google Patents

Description

G. A. REHM Nov. 4,'1958 SUPERHEATER Filed NOV. 26, 1954 Unitedv 2,858,809 SUPERHEATER Gustav A. Rehm, Springfield, Ill., assignor to Springfield Boiler Company, Springfield, Ill., acorporation of y'Illinois Application November 26, 1954, Serial No. 471,213

" 3 Claims. (Cl. 122--476) This invention lies in the iield of boilers and superheaters therefor and is generally a new improved boilerv reducing the cubicle space where the superheater elements are located.

Another object is a superheater constructed so as to increase the rate of heat transfer between the4 gas and the superheater elements ydue to an increase in the contact area exposed to the gas ow.

Another object is a superheater composed of a plurality of looped or coil tubes which are doubled back so Ias to be more compact than the usual"superheater structure.

Another object is a doubled back superheater structure of the above type each loop of which is disposed at approximately a 45 degree angle with relationto the gas ow to expose the'maximum contact area.v

Another object is a boiler structure with a superheater arranged so as to have the equivalent heat transfer area of a nned tube-type superheater.

Other objects will appear from time to time in the ensuing specification and vdrawings in which:

Fig. l is a side sectional View showing my new and improved boiler structure and superheater arrangement with parts eliminated for clarity; and

Fig. 2 is a top View of the superheater structure shown in Fig. 1.

In Fig. 1 a boiler housing is indicated generally at 10 y and includes a front wall 12, a top Wall or roof 14, a rear wall 16, two side walls 18. The housing encloses a combustion chamber or furnace space 20 defined by the side walls, the front wall and an intermediate upright bale wall 22. This baffle terminates short of the roof or upper wall as at 24 to provide communication between the combustion chamber and a gas path. Any suitable source of heat can be used with the combustion chamber, for example liquid fuel nozzles as at 26, a Stoker or gas burners, not shown.

The other portion of the housing is a gas path which follows the arrows shown in the drawing. The gas ow from the combustion space or furnace is initially turned downwardly by a depending baille 28 and after passing under the lower end of the depending baille, it flows upwardly through a tortuous path caused by a plurality of projecting baffles 30 to a suitable gas outlet 32.

`The boiler includes an upper drum 34 and a lower drum 36 interconnected by the usual circulation tubes 38 with a steam outlet at 40 on the upper drum. The

Patent i ice Patented Nov. 4, 195s upper drum has Aan internal baille' structure indicated generally at 42 which has not been shown or described in detail as it forms no part of the present invention. The usual water wall tubes 44 line the combustion space and lead to the upper drum with a group of screen tubes 46 against the intermediate baffle or wall 22 which project outwardly in staggered relation as at 48 across the top of the combusion space through the gas path and then return to the rear of the housing along the top wall or roof to the upper drum 34.

The space 49 between the screen tubes 48 and the depending baffle 28 can be generally considered as a superheater space. A superheater` manifold or bundle, designated generally` at 50, occupies this space..

The superheater is composed ofV a plurality of tubes disposed generally parallel to the gas iiow and also generally parallel to each other. Each tube connects to the upper drum at one end, at 52, and to an outlet manifold 54 at the other end. `The outlet manifold has a suitable steam outlet 56. The tubes each connect to an intermediate manifold 58 which in effect forms a part of the superheater circuit. In a sense theA intermediate manifold dividesrthe tubes intotwo sections or groups 59 and 60.v y

The steam is withdrawn from Vthe top of the upper drum at 52 and is passed through the coiled tubes where to the upper drum and the intermediate manifold 58 itis additionally heated and then out through the outlet manifold 54. The direction of ow of the steam is against the gas ow, with the steam at its hottest point at the outlet manifold 54 being in contact with, the

hottest gases, v

Each of the superheater tubes between its end is formed as a coil which is elongated downwardly to expose the maximum area of the tube to contact with the hot gases.

Each tube is formed in two sections, one being connected and the otherbeing connected from the intermediate is completely within the gas path and not in the combustion chamber, while the second group is at the upper end of the combustion chamber in a position across the outlet between the top of the intermediate batlie or wall 22 and the roof.

It should be noted from the drawings that each turn of the coils is doubled back so as to overlie each previous turn. At the same time each coil is twisted slightly sideways or canted, as shown in Fig. 2, so that each turn will be disposed at a lateral angle 62 of approximately 45 degrees to the gas flow. In Fig. 2 it can be seen that each tube would have a coiled appearance from the direction of gas ilow as well as from the side as shown in Fig. 1. Thus a maximum amount of the surface of the tube will be exposed to the gas. The turns uniformly vdiminish in length in the direction of steam flow, as shown in Fig. l, so that each group or section takes on a diminishing or converging appearance against the direction of the gas ow.

In Fig. 2, each coil is inserted between adjacent screen tubes which greatly facilitates removal and repair. For example, if one coil is defective or leaks, it could be disconnected at each of its ends and removed.

It will be noted that each superheater tube is made up of a plurality of reversely bent coils. The coils have tube legs interconnected by preferably integral return bends. The legs of a coil are elongated in a direction generally transverse to the flow of gases. It is important that the legs of one coil overlap the legs of the adjacent coil or coils. Note this relationship in Figures l and 2. Also, each coil is spaced from its adjacent coil or coils in the direction of gas ow. For example, note in Figure 2 the arrow designated-part of the angle 62 might be consideredk to represent the general direction-ofgas- How. The coils are accordingly spaced from each other generally in the direction of the arrow.

The--tube legs overlap-and-theamount of this overlap.Y

isfgenerall-y uniform, either equal or increasing or decreasing, yas the casemay-be, or a combination of increasingdecrea-sing 4might bel used. The spacing, inthe direction of gas flow, as set forth with reference figure 2, is also looped over each other or doubled back sothat a-greatery length of superheatertube can be positioned-in the same superheater space.

By this arrangement, better control ofthegas flow can be acquired over the superheater'tubes. time, the steam mass ilow can be increased. The gas mass flow can also bev increased. To'lacquire'thesameoutput or capacity from the superheater, thesuperheater space can be reduced asl compared to conventional superheaters. The doubling back of the tubes upon eachother in the overlapped arrangement of each turnwithY relation to its preceding turn gives more total contact areaof superheater tubes. Thus the heat transfer between the hot gases and the steam in the superheater willV be increased. At the same time, the turns are disposedlat a lateral angle. All of the bent portions atthe bottomand top of the turns are in a stepped relation to each other so that a maximum amount of heat transfer area isexposed.

I have found that this type of superheater arrangement is the equivalent in heat-transfer areavof, a rmed tube superheater as it permits a greater length of total tube to be positioned in the same superheater space.

It will be realized that whereas I have describedand illustrated a practical and operative device, nevertheless many changesmay be made in the size, shape, number, and disposition of parts without departing from the spirit At the same" of my invention. I, therefore, wish my description and drawings to be `Vtaken-as in a broad sense illustrative or diagrammatic, rather than as limiting me to my precise showing.

I claim:

l. In a boiler structure, a housing having a combustion space, a gas passage connecting to the combustion space and leading to a hot gas outlet, and a superheater positioned generally at the junction of the combustion space and gas passage and including at least one superheater tube," each tube havingl an. inlet and an outlet and a plurality of reversely bent coils between the inlet land outlet made up of a plurality of generally parallehelongatedv tube legs interconnected by integral return bends, each such coil being elongated in a direction generally transverse to the ow of hot gases from the combustion space, the legs of one coil overlapping the legs of each adjacent coil, each coil beingspaced from each adjacent coil in the direction of gas flow, the amount of overlap and'spacing from one coil to another beinggenerallyvfuniforrn; each tube leg of a coil being aligned between-the tube legsof each adjacent coil.

2. The structure of-claim 1 further characterized'in that. each-tube,- as aV unit, is tapered and convergent in a direction against the general direction of gas flow;

3. The structure of claim 2 in which the inlet for each tubeis downstream of the outlet, in the direction of gas flow, such that the direction of steam ow through the superheater tubes will be against the direction of hot gas flow.

References Cited yin the tile of this patent UNITED STATES PATENTS 1,653,028 Whittington et al Dec. 20, 19,27 1,887,754 Geoghegan Nov. 15, 19,32 2,157,751 Dyer et-al May 9, 1939 2,158,508 Kuhner May 16, 1939 2,252,071 Gay Aug. l2, 1941 2,354,059 Rehm Jui-y 18, 1944 2,403,237 Powell et al July 2, 19.46

FOREIGN PATENTS 208,350 Great Britain Dec. 20, 1923 169,925 Germany Apr. 21, 1906

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