Title:
Fluid heat exchange installation
United States Patent 2354222


Abstract:
This invention relates to fluid heat exchange installations, and more particularly to a tubeto-tube wall or baffle construction for a furnace, or for a gas pass. The invention may be considered as exemplified by a plurality of steam heating tubes closely arranged and disposed in row alignment...



Inventors:
Rolfe, Shellenberger
Application Number:
US42156541A
Publication Date:
07/25/1944
Filing Date:
12/04/1941
Assignee:
BABCOCK & WILCOX CO
Primary Class:
Other Classes:
122/6A
International Classes:
F22B37/20
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Description:

This invention relates to fluid heat exchange installations, and more particularly to a tubeto-tube wall or baffle construction for a furnace, or for a gas pass.

The invention may be considered as exemplified by a plurality of steam heating tubes closely arranged and disposed in row alignment so as to define a furnace or gas pass wall.

One object of the invention is to provide means whereby the wall tubes will be maintained in their wall formation with a minimum of uncooled metallic supports.

Another object of the invention is to accomplish the desired results and at the same time provide a tube-to-tube wall which includes adequately cooled all-metal closures, or gas seals, supported by the successive tubes.

The invention is particularly adapted for radiant heaters of the wall tube type when employed as walls separating series connected gas passes. When such heaters are employed as steam superheaters or reheaters the high temperatures to which the tubes are subjected are apt to cause conditions of unbalance. Such conditions may arise when steam flow through the tubes is re- 21 duced while the exposed portions of the tubes are still receiving abnormal amounts of heat from furnace gases. Such conditions are apt to cause distortion of the tubes or such bending of some of the tubes relative to adjacent tubes that gas 3s leakage develops in the wall formed by the tubes.

Such results are to be particularly avoided in a tube-to-tube wall construtcion consisting of metallic elements only and so disposed in a boiler setting that the wall divides two gas passes ar- 3 ranged in series. In this arrangement, the wall is subject to a draft differential from one side to the other and this has a tendency to cause a gas flow through the inter-tube spaces or gaps.

Such gas flow, or gas leakage, when a tube-to- 4 tube wall is employed in a steam generating installation, would not only cause the heat application to the individual tubes to be abnormal, but it would involve such by-passing of the gases, that the thermal performance of the convec- 4 tion surface of the installation would be undesirably affected, and would result in a decrease in effciency of the Unit. It is a further object of the invention to provide a specific tube wall construction which will substantially eliminate such undesiable effects.

The invention will be described with reference to the accompanying drawings, and further objects of the invention will appear as the description proceeds.

In the drawings: Fig\ 1 is a vertical section of a steam generating intallation in which an embodiment of the invention is incorporated: Fig. 2 is a partial elevation of the illustrative wall construction; Fig. 3 is a horizontal section on the line I-3 of Fig. 2; Fig. 4 is a horizontal section on the line 4-4 of Fig. 2, on an enlarged scale; Fig. 5 is a horizontal section similar to Fig. 4 taken at the position of line "-I of Fig. 2; Fig. 6 is a view in the nature Of a side elevation of the wall indicated in Fig. 2; Fig. 7 is a detail.view showing on an enlarged scale the manner in which the steam heater tubes are secured to the tie-bars; Fig. 8 is a horizontal section on the line I-I of Fig. 7; Fig. 9 is a detail view indicating a wall construction in which round rod sealing elements are employed; Fig. 10 is a detail view illustrating the manner in which the reheater wall tubes are supported; Sand Fig. 11 is a partial rear elevation of a tube-totube wall such as indicated in Fig. 9.

The illustrative wall construction is employed as part of a reheater, and it separates the gas o pass IS of a convection section 12 from the second open pass 14 of the steam generator shown in, Fig. 1. This installation includes a furnace IS, the walls of which are defined by steam generating tubes connected to the upper and lower drums II and 20. Other steam generating tubes similarly connected to these drums define the walls 22 and 24of the first opei pass 26. This gas pass, receives furnace gases kt its lower end from the combustion chamber It and discharges 0 them into the second open pas 14 at the upper part of the installation. The furnace is fired by one or more pulverized fuel burners 31.

Steam separated from the water in the daum IS passes through the tubular connections 32 L6 to the inlet header 34 of a convection superheater which includes the tubular sections 36--3 disposed across the path of the furnace gases in the gas pass II.

From the outlet header 41 of the first superi0 heater, steam passes through a pipe 42 to the inlet header 44 of a second superheater and thence through the superheater tubes 46 to the outlet header 48. From the latter the steam passes to a turbine or other unit.

I The illustrative wall between the open pass 14 and the convection section 12 is formed by reheater tubes 50 (also 50', 50", and 50'"), connecting the headers 52 and 54. The header 52 is connected to pipe 56 which conducts steam to a succeeding turbine stage. For further particulars with reference to the steam flow path of the steam generating installation, reference may be made to assignee's co-pending application Serial No. 348,623, filed by Ervin G. Bailey, on July 31, 1940.

The spaces between adjacent tubes 50-50'" may be provided so that when the tubes are heated to high temperatures, the tubes may expand, and at least a substantial part of that expansion is taken up in the inter-tube spaces thereby minimizing any accumulative increase in the transverse dimension of the wall defined by the tubes. For this reason, the proper seals between the end tubes of the wall and the outside walls of the casing of the steam generating installation may be effectively maintained, The illustrative tube4to-tube wall thus presents, a metallic face for radiant heat absorption, aud yet, in itself, provides for the normal change in the tube diameter due to change in temperature.

At the same time, the expansion spaces are arranged for sealing by accumulation of dust or slag which would tend to flow through the spaces (under starting-up conditions) on account of the draft differential between the opposite sides of the wall.

When the illustrative wall is employed as a part of a steam heater, it may operate at high temperatures, and the expansion changes are of considerable moment, although the steam pressure may be relatively low. Such expansion changes are particularly difficult to handle in an arrangement where the tubes form a gas tight wall. The temperature of the steam passing through the tubes may be as high as 1000* F., and there may be differential temperatures between the tubes of the order of 100" F. Such temperatures, and high pressure conditions, may be accompahied by a 'drafti differential of the order of 5" of water between the two sides of the wall.

The difficulties of maintaining desirable operaive conditions over a wide temperature range are also increased when the tubes are of relatively small diameter and of increased flexibility and fairly low wall thickness.

Alternate tubes such as 50' and 50" are secured to a tie-bar or channel 60 by means of lugs such as 62 and 64 welded to the tubes. The lugs extend through openings 66 in the tie-bar and are provided with vertically extending openings 68 adapted to register with slots 70 in the flanges of the tie-bar 60. When the tubes are assembled in operative relation to the tie-bar, locking rings 72 are positioned upon the lugs 64 (as indicated in Fig. 6), and locking pins 74 are inserted through the openings 68 to hold the rings in place so that they may contact the web 76 of the channel 60 and prevent any substantial movement of the tubes away from the tie-bar.

Intermediate tubes such as the tubes 50"' of the reheater are prevented from having any substantial movement out of the plane of the wall by lateral sealing members welded to the tubes. In the wall zone "A," such sealing members are shown as the bars 80-982 welded to the right hand sides of the tubes in the manner particularly indicated in Figs. 3 and 4. These bars extend from the attached tubes to positions wherein they may contact the adjacent tubes rearwardly of the plane of their centerlines. W├Żen the tubes are - cold the free edges of the bars may be slightly spaced from the adjacent tubes, but under normal operating temperatures, the preferred condition is that they contact those tubes.

In the reheater wall zone "B" (next adjacent the zone "A") similar sealing members 90-I2 are welded to the left hand sides of the tubes, and they similarly extend across the inter-tube spaces so that they may contact the adjacent tubes rearwardly of the plane of their centerlines. With this arrangement it will be observed that any force tending to move the tube 50' (Fig. 5) in the direction of the arrow 94 out of the plane of the wall, will be resisted by pressure on the tube 51" by the sealing members 90--92 secured to the adjoining tube 50'. Any tendency of the tubes 50" to move in an opposite direction is restrained by pressure of the members 80-82 on the adjoining tubes 50'. Similar effects involving the remaining tubes and sealing members maintain all of the tubes in their operative positions.

The bars (or sealing members 80-82 and 90-92) extend obliquely with respect to the plane of.the wall, and there is a clearance between the face of each bar and the adjacent tube, in the cold position. Yet the gap in the direction of the centerline of the row of tubes is greater due to the angularity. Thus, provision is made for the individual expansion of the tubes or for irregularity in the outside dimensions of the tubes.

The gas flow gap from the face of the tubes (when the wall is cold) tapers, and this is conducive to the quick accumulation df dust and/or slag to effect a proper sealing under operative high tempierature conditions, and it tends to prevent blocking of the diametrical expansion of the tube into the inter-tube spaces by slag or dist accumulations.

The angularity of each of the sealing members with respect to the external wall of the tubes to which it is secured also provides an advantageous groove for the deposition jf ,weld metal This groove may be referred to as thin, and it is this characteristic which reduces the amount of Weld metal to be deposited, and, what is more important, reduces the local stresses in the tube metal due to welding. This is particularly important when the tube walls are thin. The bars or sealing members I-82I and 9o--2 0 are also so positioned that they are effectively shielded, from radiant heat in the portions of the bars most remote from the tubes to which they are welded. Each bar is also in close heat transfer relationship to the tube adjacent its free edge. Both of these conditions, tend to keep the sealing members at such relatively low temperatures that there will be no deterioration of the metal. Stresses on the tube walls over the areas of detachment of the bars are also limited.

The embodiment of the invention illustrated in Figs. 9 and 11 includes round rod sections 1i-113 between adjacent tubes. Theyare secured in alternation (as indicated by the welds I I-118 in Fig. 11) to adjacent tubes-and are otherwise arranged in a manner similar to the above described sealing members. However, the round rod sections provide for improved "fairing up" between the tubes and they also provide for an added reduction in the amount of weld metal necessary to secure them to the tubes.

The reheater wall is associated with the upright portions 10 of the superheater tubes by looped rods 112, the ends 114 of which are bent into vertical positions so as to extend through openings i10 In the flanges of the tie-bar II.

A similar reheater wall and tie-bar construction may be employed at III (see Fig. 1) where the superheater tube portions between the superheater sections 31 and 38 are located.

The tubes (I, 80', 55", etc.)' of the reheater 6 wall may be supported from the header 34 in the manner indicated in Fig. 10 of the drawings.

This disclosure includes the elements 121, 122, and 124 of a hanger by which the tube 5l is suspended. Reheater tubes adjoining the tube thus suspended may be effectively supported by the sealing members between these tubes. By reason of the particular construction and arrangement of these members they may by their end bearings provide adequate dead weight supports for some of the reheater tubes without undesirable effects upon their other functions.

Thus, not only are original installation costs reduced by a decrease in the number of hangers necessary to support the wall, but also, better 2( maintenance characteristics are afforded.

Although the invention has been described with reference to the details of the particular embodiments shown in the drawings, it is to be appreciated that the invention is not limited to all of 2 these details The invention is, rather, to be regarded as of a scope commensurate with the scope of the subjoined claims.

What is claimed is: 1. In a fluid heat exchange installation, closely 3 arranged fluid conducting tubes arranged to present a wall exposed to the heat of furnace gases, restraining means limiting separation of the tubes in the plane of the wall, and a plurality of metallic elements disposed within channels 3 substantially defined by adjacent tubes and substantially closing off the inter-tube spaces laterally of the plane of the tube centerlines, the elements within each of said channels being arranged in end-to-end relationship with each ele- 4 ment secured to one tube only and successive elements secured to different tubes.

2. In fluid heat exchange apparatus, a row of closely spaced parallel tubes connected into a fluid system and arranged to define a wall or other boundary of a furnace gas space, the facing surfaces of adjoining tubes substantially defining V-shaped channels on opposite sides of a plane common to the tube centerlines, supporting means for at least some of the tubes, and metallic members substantially closing the intertube spaces exteriorly of said plane and maintaining the tubes in their wall forming arrangement, said members alternating either singly or in groups as to their securement to one or the other of two adjacent tubes and extending from their supporting tube into close proximity to an opposing surface of te the adjoining and facing tube, successive members longitudinally of the channels having end-to-end contact whereby relative longitudinal movements of adjoining tubes are limited.

3. In combination, a row of closely adjacent tubes connected into a fluid system and arranged to define a wall for a furnace gas space, parts of the facing surfaces of adjoining tubes substantially defining V-shaped channels on opposite sides of a plane defined by the tube centerlines, and short metallic members secured in rows longitudinally of the tubes and disposed externally of said plane with at least their major portions within the channels opening away from the furnace gas space, successive members within any one of the latter channels alternating with respect to their securement individually to one tube only with their free opposite surfaces disposed in close proximity to the adjoining tube.4. In fluid heat exchange apparatus, closely spaced tubes projected into a fluid system and arranged so as to define a wall of a furnace gas space, transverse tie-bars on one side of the wall, means for securing some of the wall tubes to the tie-bars, and rows of metallic sealing strips or bars disposed in longitudinal arrangement between adjacent tubes, some of said strips or bars between the same adjacent tubes being welded to the same tube and disposed so as to almost contact the adjacent tubes-beyond the plane of their centerlines, others of the bars or strips between Sthe same tubes being welded to the other of the tubes and disposed so as to be similarly closely related to the first tube, said bars or strips being set back rearwardly from the plane of the centerlines of the tubes.

5. In fluid heat exchange apparatus, a plurality of closely spaced tubes disposed in wall formation and exposed on one side to the heat of furnace gases, and spaced metallic projections secured to the facing sides of adjoining tubes to prevent movement of the tubes from their wall formation and to substantially close the spaces between the tubes, the spaced projections on each of said adjoining tubes extending into the spaces between successive projections from the other of said tubes, 0 said projections also extending from their supporting tubes into positions wherein they will engage the et e next tube to prevent excessive relative movement of the tubes in directions normal to the face of the wall.

S6. In fluid heat exchange apparatus, a plurality of closely spaced tubes disposed in wall formation and exposed on one side to the heat of furnace gases, and metallic strips secured at longitudinally spaced positions to the facing sides 10 of adjoining tubes and substantially closing the inter-tube spaces, said strips being also disposed rearwardly of the centerlines of the tubes for maintaining the tubes in.their wall formation, the spaced strips on each of two adjoining tubes extending transversely beyond the inter-tube space and into the spaces between successive strips on the othe of said tubes.

7. In a fluid heat exchange apparatus, a gas pass wall including closely adjacent tubes con5O nected into a fluid system, and metallic closure members extending longitudinally of the tubes with two sets of the members between each pair of adjacent tubes, one ofai said sets being secured only to one of the adjacent tubes while the mem55 bers of the other set are secured only to the other of said tubes, all of said members being disposed at positions offset from the plane of the tube centerlines and being of such size or so disposed that they extend from their supporting 60 tubes a distance greater than the minimum space between the adjacent tubes to maintain the tubes in their wall arrangement.

8. In .fluid heat exchange apparatus, a tubeto-tube wall connected into a fluid system and 65 separating two series connected heating zones ,between which there is a pressure differential, the successive tubes of the wall having a minimum spacing only slightly more than the diametrical expansion of a tube over the tempera70 ture range of the apparatus, metallic space closure members secured to the quadrants of the tubes remote from the first of said zones and extending across the intertube spaces, some of the closure members int each Intertube space being Sts secured to one tube and extending to a position wherein they are close to the adjoining tube, an others of the closure 'members in the same in tertube space being reversely secured and ar ranged relative to the adjoining tubes, sali members substantially closing the spaces be tween the tubes and forming outwardly taper ing ash or slag receiving pockets with adjacen surfaces of the rear quadrants of the tubes.

9. In fluid heat exchange apparatus, tubes ar ranged to define a wall subject on one side tA furnace gases, the tubes having a wall spacin only slightly greater than their diametrical expansion, two sets of metallic closure members be. tween each pair of successive tubes, said members being secured to the rear quadrants of the tubes, one set of said members being secured only to one of said tubes while the members of the other set are secured only to the adjoining tube, each of said members extending from its supporting tube into close proximity to the opposing surface of the adjacent tube, a tie-bar extending across the tube defined wall, means securing at least some of the tubes to the tie-bar, and means connecting the tubes into a fluid system.

10. In fluid heat exchange apparatus, a row of tubes closely spaced in the plane or zone common to their centerlines and arranged to define a wall exposed on one side to the heat of furnace gases, the spacing of the tubes in the row being such that the tube metal constitutes almost the entire furnace gas face of the wall at operating temperatures, a wall support, means for securing some of the tubes to the support, and separate metallic sealing members secured to all of the tubes rearwardly of said plane or zone and maintaining the remaining tubes in wall arrangement, each tube having the sealing members extending from opposite sides thereof with some of said members spaced longitudinally of the tube so that they afford spaces for the disposal therein of similar members secured to a succeeding tube.

11. In a superheater or reheater, a row of wall tubes subject externally to the heat of furnace gases, means connecting the inlet ends of the tubes to a source of steam, rows of closure members secured to the facing sides of adjacent tubes and disposed back of the common plane of the tube centerlines relative to the furnace gases, some of said members being secured to one of each pair of adjacent tubes while others of the members are secured to the other tube of each pair, all of said members being disposed longitudinally of the tubes and extending from their supporting tube into a position where they may contact the adjacent tube to prevent abnormal movement of the tubes from their wall forming relationship.

12. In a fluid heating installation, tubes defining a wall exposed on one side to the heat of furnace gases, the tubes being closely spaced with surfaces of adjacent tubes substantially defining V-shaped channels on opposite sides of a plane determined by the tube centerlines, means connecting the tubes into a fluid system, and coacting space closing and tube interlocking members disposed in the channels remote from the furnace gas face of the wall, some of the members in any one channel being secured to one tube and extending across the channel with their free 7 edges in proximity to the surface of the adjoining tube while the remaining members in the same channel are reversely arranged with respect to their relationship to the adjoining tubes.

13. In a fluid heating installation, tubes de- 7 d fining a wall exposed on one side to the heat of furnace gases, the tubes being closely spaced with S surfaces of adjacent tubes substantially defining d V-shaped channels on opposite sides of a plane - 5 determined by the tube centerlines, means conS necting the tubes into a fluid system, tie-bar t means to which some of the tubes are secured, and co-acting closing members disposed in the chan- nels between the tie-bar means and said plane, g 10 some of the members in any one qhannel being r secured, to one tube and extending across the channel with their free edges in proximity to the surface of the adjoining tube while the remaining members in the same channel are reversely arranged with respect to their relationship to the adjoining tubes, said members co-acting with the adjoining tubes to form ash receiving pockets with their opposite sides converging toward the furnace gas face of the wall.

14. In fluid heat exchange apparatus, a row of tubes closely spaced in a plane or zone common to their centerlines and arranged to define a wall exposed on one side to the heat of furnace gases, the spacing of the tubes in the row being such that the tube metal constitutes more than 95% of the entire furnace gas face of the wall at operating temperatures, a wall support, means for securing some of the tubes to the support, and separate metallic sealing bars secured to all of the tubes rearwardly of said plane or zone and coacting with the support to maintain the remaining tubes in wall arrangement, each tube having its sealing bars extending from opposite sides thereof obliquely to a plane tangent to the tubes at one side of the wall, some of said bars being also spaced longitudinally of the tube so that they afford spaces for the disposal therein of similar bars secured to a succeeding tube.

15. In a tubular wall construction for fluid heat exchange apparatus, a plurality of closely spaced tubes connected into a fluid system and disposed so as to define a wall for heating gas space, and intertube sealing elements spaced longitudinally of each tube and secured on opposite sides thereof and extending into close proximity to adjoining tubes, the sealing elements extending from adjacent tubes being so related that the sealing elements from any single tube extend into the spaces between successive sealing elements secured to adjoining tubes, said sealing elements being offset from the plane of the centerlines of said tubes and extending from the tubes a distance greater than the tube-to-tube spacing.

16. In a fluid heating installation, tubes de5 fining a wall exposed to the heat of furnace gases, the tubes being closely spaced with surfaces of adjacent tubes substantially defining V-shaped channels on opiobsite sides of a plane determined by and common to the tube centerlines, means 10 connecting the tubes into a fluid system, tie-bar means to which some of the tubes are secured, and co-acting space closing and tube inter-locking members disposed in the channels and between two parallel planes tangent to the tubes toward 5 opposJte sides of the wall and parallel to said tube center-line plane, each of said interlocking members being directly and rigidly secured to one tube only and arranged so as to permit adjacent tubes to have limited relative movements while 0 maintaining the tubes not secured to the tie bar means in substantial wall forming relation to those tubes which are so secured.

17. In a steam generator having an open pass disposed between the furnace and a convection s section, means including steam heater tubes in a substantially tube-to-tube wall arrangement for separating said open pass from the convection pass, and tube aligning and space closing metallic members carried by the steam heater tubes and substantially sealing the wall between the convection pass and the open pass without the use of non-metallic refractory in that wall, said metallic members maintaining the integrity of the wall without rigidly securing adjacent tubes to each other.

18. In a tubular wall construction for fluid heat exchange apparatus, a plurality of closely spaced tubes connected into a fluid system and disposed so as to define a wall exposed to heat, means for suspending some of the said tubes, and intertube sealing elements spaced longitudinally of each tube and secured on opposite sides thereof so as to extend into close proximity to adjoining tubes, the sealing elements extending from adjacent tubes being arranged for end to end contact and so related that. the sealing elements from any single tube extend into spaces between successive sealing elements secured to adjoining tubes, said arrangement of sealing elements being thus adapted to act as dead weight supports for tubes adjacent a suspended tube.

ROLFE SHELLENBERGER.