US2119451A - Superheating apparatus - Google Patents

Description

May 31, 1938.

51 1 i l i i l i i j i C. s. TURNER SUPERHEATING APPARATUS -Filed June 29, 1936 2 sheets-s eet 1 mvn no'n CHARLES S. TURNER ATTORNEYS May 31, 1938. 'c. s. TURNER SUPERHEATINQ APPARATUS Filed June 29, 1936 2 sheets-sheet? v FIGS.

mvsm -on CHARLES $.TURNER ATTO RN EYS Patented May 1938 UNITED Y'STATES PATENT OFFICE-1' 1s Claims.

This invention relatesto the superheating of steam, and is particularly directed to improve: mentof the process and apparatusdisclosed in my PatentNo. 2,000,906, issued May 14,- 1935.

Superheaters constructed and operated in accordance with the disclosure of the patent men-, tioned are of the radiant type, and may be directly exposed to radiation in the hottest portions of the boiler. They incorporate steam and water tubes integrated throughout their exposed length. as by welding. In normal operation, the watt. carried at a reduced level in the water passage or passages, and the level 'is controllable by an inlet throttle valve to regulate the temperature of the superheated steam. The tube assemblies are of course arranged in other than horizontal position, in order to facilitate such control. When thesteam tubes are empty, as in starting the boiler, the water tubes are flooded, and their heat-absorbing power protects the steam tubes against burning out, while when the water is at reduced level in the water tubes, such tubes are protected by the saturated steam generated in them and by the excess heat absorbing capacity of the steam tubes. I have found it desirable, in the construction of such superheaters, to arrange where possible for disposition of the steam tubes upon the outside of the assembly, in order that an active superheating surface area as great as possible may be presented to the source of radiant heat. It is essential, however, if the superheating process is to be successfully carried out in accordance with the teachings of the patent, that the water tubes, when and where they contain water, be able to absorb. excess or unneeded heat from the outer, heat-exposed surface of the assembly before such heat can reach the steam, in orderto-prevent superheating in the portions ofthe apparatus below the water level. Quite naturally, the structures first conceived for. carrying out this process, involved arranging the water passages outside the steampassage or passages, in positions which appeared best calculated to intercept the heat before it could reach the steam. This, however, reduced the exposed superheating surface, due to the shielding eifect of the water tubes, even when and where empty. Unless, also, some means were provided for limiting heat conduction between the inside abutting surfaces of the steam and water conduits, the steam lost heat to'the water, and steam could not be run downwardly through the assembly without the occurrence of undesirable desuperheating below the water level. The present invention, therefore, aims to provide water regulated superheating of the type indicated, employing a plurality of steam tubes grouped about a central or substantially enclosed 1 water tube in such manner as to present a main-, mum of exposed superheating surface and,pro-,, tect the water tube when empty, yet so arranged that the water within the central water tube nevertheless efiectively absorbs heat excess or unneeded heat from the surface of the steam tubes before such heat can reach the steam within the latter. 7 Another important object of this invention is to provide in such a. superheater water and.

steam tube elements so structurally and functionally inter-related as to incorporate such inter-protective function, and allow direct heat absorption through metal-from the exterior by the internal water tube, while heatabsorption: by the water tube from. the inner shielded sur-,, faces of the steam tubes which abut the water tube is greatly restricted. Y In the drawings: Figure 1 is a diagrammatic vertical section of a boiler equipped with a radiant superheater assembly constructed, installed, and adapted to operate in'accordance with the principles of this invention. 1 g

Figure 2 is a plan view, partly broken away, of the superheater assembly, constituting a development thereof in one plane. 1

Figures 3 and 4 are cross sections takensub stantially on the lines 3-3 and 4-4 respectively of Figure 2, and looking in the direction of the arrows.

Figure 5 is a cross section similar to Figure 3 of a modified form of tube assembly, and

Figures 6 and 7 are similar cross sections of another modification, showing the same adapted to construction of different proportions.

Referring now to the drawings, reference character l0 designates the upper or steam drums of a boiler, whose walls are designated I2, and which is provided with a lower or mud drum l4, between which and the upper drums water tubes l5 are shown disposed in moreor less-conventional arrangement.

the boiler, although any substantial inclination.

from the horizontal which allows theconvenient maintenance of a water level therein will sufiice, in accordance with the desires of thedesigner of the particular installation. The tube assemblies terminate at their upper and lower ends in head-' ers 2l, respectively, to which they are welded as at 26, or otherwise suitably secured. Steam tubes 23 will be seen to open directly into the interior of each header, while a continuation of each central water tube 25 is carried through the header to a separate header passage as 24 extending along the back of the main header body.

The central water tube may be fed from the lower drum l4 by means of a pipe 21 connected to the portion 24 of the lower manifold, while the water supply is controllable by means of valves, as 2829, the former thermostatically controlled in response to the temperature of the output superheated steam, and the latter constituting a hand operable by-pass. The by-pass valve is normally closed, and the thermostatically regulated valve arranged to raise the water-level in response to a rise of output steam temperature, and vice versa, in order to maintain the output at any given temperature. At their upperends the water tubes 25 are connected to the steam spaces of drums ID as by means of a pipe 32, running to the drums from upper water tube header 24. Such steam spaces also supply steam to be superheated to the lower ends of steam tubes 23, through a pipe 34 connecting the drum and the lower steam header portion 2|, although the steam might be made to flow downward through the assembly rather than upward. The upper ends of the superheater tubes 23 discharge the superheated steam through a steam pipe Ill.

The central water tube 25 is provided with integral flutes 35, proportioned to provide concave channels adapted to receive the steam tubes 23, which are fitted therein and welded, asat 33, to the tops of the flutes. The flutes and tubes 23 are shown as'helically disposed, to render as uniform as possible the heat absorption by each tube. The peaks of the flutes extend outwardly between the steam tubes, and by the welds 33 are integrated to the outer surface of the assembly. The parts are so proportioned with respect to the maximum heat impingement to which the apparatus is to be subjected and to the minimum steam and maximum water temperatures to be encountered, that when water is contained in central tube 25, it can absorb excessive or unneeded heat from the most remote parts of the exterior surface of the assembly, including the steam tubes, before such heat can reach any steam which may be present in tubes 23, thus preventing over superheating of such steam, in accordance with the design and the relative temperature conditions. Preferably the arrangement is such, however, that when the steam tubes are empty the water can maintain all portions-thereof at safe temperatures. This will be seen to be a simple engineering problem of proportioning the flutes, tubes and welded areas in accordance with the conditions encoimtered in each installation.

The described action is possible because of the efliciency of the heat path through the flutes and the welds to the exposed exteriors of the steam tubes, while since there is no integral connection between the steam tubes and water tubes except at such externally located welds, heat transference between their internal interfltted portions is impeded to such degree that-no sub stantial heat flow is possible; The entire heat path provided by each weld is also required dur-" ing such operation to handle inflowing heat, so

of tubes 23-25 acts to virtually isolate theminsofar as heat interchange is concerned, preventing reduction of the temperature of the steam flowing through the portions of tubes 23 below the water level, while above the water level the full exposed superheating surface of tubes 23 is efiective. It will also be seen that the water tube is protected by the steam tubes when and where the former is empty, and that, as stated, due to the eflicient heat-conductive connections between the central passage and the exterior of the assembly, the steam tubes when empty are eflectively protected by the water which is then present in the water tube.

In themodified multi-tube assembly shown in Figure 5, in which analogous portions to those already described have been given like reference numerals distinguished by the addition of the letter a, the central water passage is formed of plates 25a of partly cylindrical contour, shaped to receive steam tubes 23d and partly encircling each, the edges of the plates extending outwardly between each pair of adjacent steam tubes to form flute portions 35a arranged in positions analogous to the locations of the flutes 35' of the tube assembly shown in Figure 3. Such outwardly projecting flute-forming portions of the plates are welded together and to the surfaces of the tubes between which they extend, as at 33a, and the lack of integral connection between the water tubes and plates at their other interfitted portions inside the assembly similarly prevents substantial heat flow to the central water passage except from the exposed surface, the action of course resembling that of the flrst embodiment already described.

In Figures 6 and '7 the plate portions 251) are further modified to provide concave rather than convex, inner surfaces imparting a substantially cylindrical interior to the water channel which facilitates its cleaning by ordinary Yturbining methods. Such plates may, as indicated be used in conjunction with assemblies of different numbers of steam tubes (23b) so that the curvature of the inner surfaces of plates 25b may not be strictly concentric with the axis of the assembly, depending upon the arrangement. Such eccentricity, within limits, however, does not prevent proper cleaning, enabling the adaptation of the plate units to constructions of diverse proportions, as will be readily appreciated.

While it will be apparent that the illustrated embodiments of my invention herein disclosed are well calculated to adequately fulfill the ob jects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claims.

What I claim is:

l. A multi-tubesuperheater assembly adapted to be subjected to direct impingement of radiant heat, comprising a central water tube, a plurality of substantially parallel longitudinally extending rib portions integral with and projecting radially from its exterior wall, a plurality of longitudinally extending steam tubes grouped about the water tube, one arranged in the channel formed between each pair of adjacent rib portions, the steam tubes being spaced apart by and having their exposed surfaces welded to the peaks of the 'rib portions.

2. superheater assembly as set forth in claim 1 in which the rib portions are formed by radially thickened portions of the water tube wall, and the water passage lies entirely within the the proportions of the steam tubes, defining the length of the heat paths between-the exposed exterior of the assembly and the water passage, are so proportioned to the maximum heat impingement to which the apparatus is to be sub -jected, and to the steam and watertemperatures, that cooling water in the water passage, when and where present, may absorb heat from the portions of the exterior surface most remote therefrom more rapidly than such heat may be transmitted to the steam, while the steam tubes surround the water tubes and act'to protect the latter when or where empty of water.

4. In combination with a steam boiler including radiant heating means and water-containing portions, superheating means comprising a multitube assembly directly exposed to the radiant heat and comprising a central water tube having a longitudinally fluted exterior, a plurality of steam tubes fitted into the channel's formed by said flutes and welded to the tops thereof, the steam tubes being spaced by the flutes, means for delivering steam to be superheated to said steam tubes from said boiler, regulable means for delivering water to the water passage from said water-containing portions and for maintaining a reduced and controllable water level in said passage, the welds being located at the exposed surface of the assembly and the other interfltted portions of the tubes having distinct walls acting to restrict heat transfer therebetween except at said exposed surface, the proportions of the flutes being such, and the steam tubes being so proportioned to the maximum heat impingement to which the apparatus is to be subjected, that cooling Water in the water passage, when and where present, may absorb heat from the portions of the exterior most remote therefrom rapidly enough to prevent excessive temperatures in all parts of the tube and unwanted superheating, while the steam tubes surround the water tube and act to protect the latter when or where empty of water.

5. A superheater assembly as set forth in claim 1 in which said water tube is formed of a plurality of elongated channeled elements of such external concavity as to receive the water tubes, arranged edge-to-edge, said edges projecting between the steam tubes to form the flutes and being welded together and to the steam. tubes.

throughout their length, 4

6. A superheater assembly comprising a central conduit structure having wall portions of variant thickness defining longitudinal channels upon its exterior surface, a plurality of tubes arranged in said channels, thicker. wall portions of said central conduit structure projecting outwardly between the walls of said tubes, and being welded thereto throughout their exposed' length but only adjacent exposed portions of said tubes. I

'7. A superheater structure as set forth in claim 6 in which the entire surface of said central conduit structure is shieldedby said tubes and weld ed areas.

8. A multi-conduit superheater tube assembly comprising a control conduit disposed substantially centrally and formed of a plurality of longitudinally arranged elongated elements grouped about a contained area and welded together along their edges, said elements having channeled external surfaces, and heating tube portions fitted into said channeled surfaces and welded to the elements.

9. A superheater mbly as set forth in claim 8 in which said heat ng tube portions are secured together and to the elongated elements by the welds which secure said elements together.

10. A superheater assembly as set forth in claim 8 in which said heating tube portions are secured together and to the elongated-elements by said same welds which secure said elements together, said welds forming the only integralconnection between the heating tubes and said elements.

11. A superheater assembly as set forth in claim 8 in which said heating tube portions are secured together and to the elongated elements by said same welds which secure said elements together, said welds forming the only integral connections between the heating tubes and said elements and being located upon the outside of the assembly.

12. A superheater assembly as set forth'in claim 8 in which said heating tube portions are secured together and to said elongated elements by said same welds which secure said elements together, said welds forming the only integral connections between the heating tubes and said elements and being located upon the outside of the assembly, said control conduit being completely enclosed by said welds and tube portions.

13. A superheater assembly as set forth in claim 8 in which the internal surfaces of said elongated elements are also channeled substantially partly cylindrlcally, and said last-mentioned channels, when the plates are assembled, cooperate to provide said control conduit with a substantially cylindrical internal wall.

14. A superheater assembly as set forth in claim 8 in which the internal surface of each of said elements is provided with a reentrant sub stantially partly cylindrical channel extending substantially the full width of the element;' said last nentioned channels, when the elements are assembled, cooperating to form a tubular control conduit having rounded internal walls.

15. A superheater assembly as set forth in claim 8 in which each of said elements is channeled both internally and externally, the in-. ternal channel in each being of substantially partly cylindrical form and extending substan-.

tlally the full width of the element, said internal channels when the elements are assembled cooperating to form a tubular control conduit having rounded internal walls, the external channels being upon lesser radius and adapted to hold said tubes in spaced relation.

16. A superheater assembly as set forth in claim 8 in which each of said elements is chan neled both internally and externally, the internal channel in each being of substantially partly" cylindrical form and extending'substantially the full width of the element, saidinternal channels when the elements are assembled cooperating to form a tubular control conduit having rounded internal walls, the external channels being upon lesser radius and adapted to hold said tubes in spaced relation, portions carried by said elements extending outwardly at least part way between said tubes, said'projecting portions being welded together and to said tubes.

17.. Means as set forth in claim 6 in which said central conduit structure is formed of a plurality of sections divided longitudinally in their thicker areas and'secured together by said same welded connections.

18. A multi-tube superheater assembly adapted to be directly subjected to radiant heat, comprising integratedsteam and water tube portions, the water tube portions including a central chantwo adjacent steam tube portions to a single rib CHARLISS.TURNER.

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