US2232935A

US2232935A - Fluid heater

Info

Publication number: US2232935A
Application number: US209921A
Authority: US
Inventors: Ervin G Bailey
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1938-05-25
Filing date: 1938-05-25
Publication date: 1941-02-25
Anticipated expiration: 1958-02-25

Description

E. G. BAILEY Feb. 25,1941.

FLUID HEATER .18 25 l9 v o 4 Q 5 C8) 22 Zirw'z BQHZEZTOR @QW Feb. 25, 1941. E. ca. BAILEY FLUID HEATER Filed May 25, 1938 3 Sheets-Sheet 2 coooooooooooooo O o ODmuOOoooom C. mm m mvOOOOO w o o o O O AW O Q oooooqvoooooo 0 AW d ATTORNEY.

Feb. 25, 1941. a Y 2,232,935

FLUID HEATER 3 Sheets-Shed 3 Filed May 25, 1938 00000000 OOOOOOOOOOC OOOOOOOOOEDO Err/in 6 Bailey ATTORNEY.

. tube internal conditions are not the same viously heated far below their safe operating Patented Feb.25,1941 t a r 2,232,935

"UNITED STATES PATENT OFFICE FLUID HEATER Ervin G. Bailey, Easton, Pa., assignmto The -Babcock 8; Wilcox Company, Newark, N. 1., a

corporation of New Jersey Application May 25, 1938, Serial No. 209,921 12 Claims. (Cl. 122- 328) My invention relates in general to the conthe front row of atube bank is materially afstruction' and arrangement of a bank of fluid fected by the method of fuel firing and isgreatheating tubes arranged to receive a flow of heatest when the heating gases have a velocity of ing gases transversely thereof from an assoapproach, 1. e., a velocity component normal; 5 ciated furnace or other source of, heating gases. to the tube 'bank, which is not uniform over the 5 While my invention may be embodied in various entire tube bank area. For example, in one types of heat transfer apparatus, it isparticuwell known type of marine boiler, two oppolarly designed and especially useful in the consitely inclined steam generating tube banks are struction of water tube steam boilers. symmetrically arranged relative to an A-shaped In the operation of water tube boilers having furnace therebetween fired by liquid fuel burners a bank of water tubes extending across a gas located in one of the end walls of the furnace. pass opening to a furnace, experience has shown With' this arrangement the heating gases tend that some of thetubes may rupture from overto travel longitudinally of the furnace with a heating even when clean internally. This exvelocity dependent upon the combustion rate. r perience has resulted in practices limiting the The gases must make a 90 change of direction 15 permissible operating capacity of a steam boiler to enter either tube bank. Under these conto a capacity below the point at which tube ditions there appears to be a tendency for the failures of this type are likely to occur. heating gases to concentrate in the opposite end When clean tubes fail through overheating of the furnace and the high velocity of approach 30 of the metal, it is usually found that the damof the gases in this section makes the convection aged tubes are localized as to position in a tube heating rate greater for the tube bank portion bank. Certain tubes appear to always fail benear the wall opposite thefuel burners than in fore others, and in many cases in the tubes that the tube bank portions nearer the burner wall. fail, the failure is localized at a certain position In addition the most intense combustion condialong their lengths and does not extend over tions in the furnace usually occur nearer to the the full length. In most of such cases, the tubes rear wall, so that the front row tubes near this that fail are only a small part of the total num: wall tend to receive a greater amount of heat ber of tubes in the bank, so it is apparent that by radiation than the other tubes of the front most of the tubes had not reached their limit rows. 0 of capacity at the time when the first tube to In accordance with my invention the gas flow fail exceeded its safe limit. areas between the tubes of the tube bank are The tubes in the front row of the tube bank relatively proportioned to eliminate any inequaliare morelikely to fail by overheating than others. ties in the heating of corresponding tubes in These front row tubes not only receive more heat different portions of the tube bank by regulating by radiation from the furnace than the other the distribution of the heating gases over the tubes, but in addition receive heat by convection tube bank. By my invention the convection heat- -more intensely than the others because the gases ing of any tubes in danger of overheating can contacting therewith will have the highest tembe reduced to a safe operating rate while the perature. It often happens however, that the convection heating of other tubes that were prethroughout the b nk, and that they are less limits can be substantially increased. This will favorable to tube maintenance within the more result in a greater margin of safety for a rate intensely heated tubes in the front row than in of fuel burning and some increase in steam genthe remaining part of the bank, in which case erating capacity of the tube bank as a whole, the tendency for the front row tubes to fail is because there will be a substantia ly greater num- 45 increased. her of tubes receiving an increased amount of Not only do the tubes in the front row tend to heating than the number of tubes that receive fall more quickly for the same internal condia decreased amount of heating. Conversely it tions in all of the tubes, but it commonly occurs will permit of a higher rate of fuel burning and that only afew of the tubes of the front row a substantial increase in steam generating ca- 50 fail, indicating an inequality in the rate of heatpacity without exceeding the factor of safety ing of the tubes in the front row, either by expreviously used. cessive radiation or convection heat transfer, or The various features of novelty which characboth. I have found that this localization of the terize my invention are pointed out with parzone of tube failure to certain tubes lying in ticularity in the'claims annexed to and forming 55 1y with a standing of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and' described several embodiments of my invention.

Of the drawings:

Fig. 1 is a sectional elevation of a marine type steam boiler constructed in accordance with my invention:

Fig. 2 is a section Fig.

Figs. 3 and 4 are sectional views illustrating modified tube bank constructions;

Fig. 5 is a fragmentary longitudinal section taken on the line 5-5 of Fig. 4

Fig. 6 is a view similar to Fig. 1 illustrating a modified steam boiler construction;

Fig. tube arrangement on the lines 1-! of Fig. 6; and

Fig. 8 is a transverse section illustrating the tube arrangement on the lines 88 of Fig. 6.

The general steam boiler design illustrated in Figs. 1 and 2 is of a well known marine type,

taken on the line 22 of comprising a pair of oppositely inclined banks of steam generating tubes l0 and II defining therebetween an A-shaped furnace chamber l2. The furnace chamber is closed at its front and rear ends by walls l3 and M respectively, the front wall l3 being formed with a plurality of burner ports l5 through which liquid fuel burners i6 discharge parallel streams of atomized liquid fuel and air horizontally toward the rear wall I4. The tube bank I0 is divided into transversely spaced inner and outer sections extending between a lower water drum I! along one side of the furnace chamber and'an upper steam and water drum I 8 extending along the apex of the furnace chamber. A bank of U-shaped superheater tubes I 9 are horizontally arranged between the sections of the tube bank H) with the ends of the U-tubes connected to external inlet and outlet headers 20 and 2| respectively. The

opposite tube bank ll extends between the steam and water drum l8 and a lower water drum 22 arranged along the opposite side of the furnace chamber. The tube banks in and II are constructed for a single pass gas flow transversely thereof to heating

gas outlets

23 and 24 respectively, in which suitable economizer sections 25 are located.

As previously described, in steam boilers of this type the burning fuel streams tend to travel longitudinally in the furnace chamber at a velocity dependent upon the combustion rate. The heating gases generated must therefore make a 90 change of direction to enter either tube bank. The velocity head or inertia of the heating gases will cause the gases to concentrate in the rear portion of the furnace chamber, and consequentuniform tube arrangement longitudinally of the bank and thus a uniform pressure drop transversely of each tube gases would tend to distribute non-uniformly along the tube bank, and more particularly, a major portion of the gases will tend to flow transversely of the rear half of the tube bank. With this burner and tube bank arrangement it is also found that combustion conditions in the furnace chamber are non-uniform and usually more intense in the rear portion thereof. Under these conditions the water tubes in the rear portion of the tube banks, and particularly those in the 7 is a transverse section illustrating the bank, the heating 2,232,935 a part of this specification. For a better under-- front rows of that section, may be in danger of overheating, while most of the remaining tubes in the bank are not being heated up to their safe operating limits.

In accordance with my invention, the inner sections of the tube banks l0 and II are constructed with a tube pattern to provide a distribution of the heating gases relative to each tube bank of such a character that a substantially uniform, heating of all of the tubes in the same longitudinal row of each tube bank will result. In Fig. 2 I have illustrated the tube arrangement for the inner sections of the tube banks In and II. As shown, the inner section of the tube bank I0 is formed by five longitudinal rows of staggered tubes of uniform diameter. All of the tubes in each longitudinal row have the same spacing, but the transverse spacing of plied to the superheater by spacing the superheater tubes in groups with a progressively decreasing gas flow area across each group towards the rear end of the superheater and closing the space between the groups.

Similar results can also inner sections of the tube shown in Fig. 3 or Figs. 4 and 5, the illustrations being for a tube bank corresponding in location to the tube bank l0 in Fig. 1. In Fig. 3 the tube bank construction employs a variation both in tube size and spacing. The two inner or furnace row tubes l0 are of uniform diameter and staggered relation. The tubes in the remaining three rows are divided into three outer distinct groups longitudinally of the bank. The tubes l0 of the group adjacent the front wall are of smaller diameter than the tubes I 0" and spaced on'similar centers. The tubes ill of the group intermediate the length of the bank are similar in diameter and spacing to the tubes Ill providing a decreased gas fiow area thereacrossin comparison to the gas flow area through the tube rows l0". The tubes I of the group adjacent the rear wall are similar in diameter, but more closely spaced longitudinally than the tubes I0". With this arrangement the free gas flow area will successively decrease from the front end of the tube bank to the rear end.

In Figs. 4 and 5 a second modified construction of the inner section of a tube bank is illustrated. In this tube bank design the two inner or furnace rows of tubes 26 are of similar diameter and spacing and the three outer rows 26 of smaller diameter but of similar spacing throughout. The desired variation in gas flow area longitudinally of the bank is secured byvarying the effective area of they intertube spaces of the outer tube rows 26. As indicatedin Fig. 5 the tubes 26' in the tube bank section adjacent the front wall l3 have unobstructed-intertube spaces. The intertube spaces of the tubes 26 in the intermediate and rear sections of the bank however, are partly obstructed by integral projecting laterally into the intertube spaces. The intertube-spaces of the rear tube section are made more obstructed than the intertube spaces of the intermediate tube section by a closer vertical spacing of thestuds, as shown in Fig. 5.

be secured with the metallic studs 26 banks constructed as Figs. 6, 7 and 81 illustrate the embodied in another well known type of steam boiler adapted formarine'useg Infthis boiler two oppositely inclined banks of'steam generating tubes 33 and 3| are arranged between a steam andwaterdrum 32 respectively at oppositesides of the setting. The mud drum 34 is arranged at a higher elevation than the drum 33 and the bank 3| given a. lesser inclination than the bank 3ll. Each of the tube banks is divided into inner and'outer tube sections with the sections of the bank spaced sufficiently to permit the installation of a group of steam superheater tubes therebetw'een. The

tube banks are arranged for a single pass gas flow. transverselythereof, with thegases passing over the banks 33 and 3| exiting through gas outlets 35. and 36 respectively. The 'A-shaped furnace 31 defined by the tube banks'has a vertically inclined wall 38 below the drum 34, and

through which liquid fuel burners 33 discharge.

The fuel burners 39 are arranged along the full length of the furnace in a position causing the heating gases to be directed toward the lower part of the tube bank 30. The velocity of the heating gases-is relatively high, so that their inertia would ordinarily cause a greater convection heating of the tube bank3|l than of the bank. 3|. With the described arrangement a portion of theheating gases will tend to enter the tube bank 30, pass upwardly therein, and then outwardly into the upp r portion of the bank 3|, causing the intermediate and lower portions of the front rows of tubes in the bank 30 and the upper portions of the front rows of tubes in the bank 3| to be more intensely heated than the other tubes of the banks.

In accordance with my invention a more uniform heating of the banks 30 andfl3| and of all portions of the remaining tubes 30 and 3| in each of the inner sections are of smaller diameter. The tubes 30 have their lower and intermediate portions close- 1y spaced and arranged as shownin Fig. 7 relative to the intertube spaces 'of the larger diameter tubes so as to decrease the gas flow area through those portions of the tubebank. The upper portions of the tubes 30 are'more widely spaced, as shown in Fig. 8, to provide a larger gas fiowarea through that section as compared to the intermediate and lower portions of the inner section of the bank. With this arrangement a larger portion of the heating gases will be deflected towards the tube bank 3| and a' more equal division of the gases between the tube banks thereby effected as well as amore uniform distribution of the gases the tube bank 30.

A similar arrangement of the tubes 3| is employed to secure a more uniform distribution of the gases throughout the height of the tube bank 3|. For this purpose the upper portions of the tubes 3| are arranged substantially as shown in Fig. '7, while the lower portions of those tubes are arranged as shown in Fig. 8. By this arrangement a larger portion of the heating gases entering that tube bank willbe forced to pass across the lower portion thereof.

Where the weight of the boiler is of primary importance, as in a marine installation, the desired heating gas flow can be best obtained by invention as and mud drums 33 and 34- tubes therein is accomplished by arranging the tubes in the inner sections of those throughout the height of,

with my invention. If desired, spacers or connections may be employed tubes to avoid any change in the original arrangement under operating conditions. The optimum tube arrangement can be determined generally by calculation, and the calculated arrangement checked by measurement of the variations in drum position in operation, or by measurement of individual tube temperatures by means of wires of predetermined fusion temperature stretched between the tube ends and examination of such wires after a period of known operating conditions to determine whether or not such tubes have exceeded their desired maximum temperature. The various tube bank constructions disclosed effectively neutralize of an unsymmetrical fuel burner location and the operation of the boiler with a larger number of tubes absorbing heat at the maximum heat absorption rate which they can safely withstand substantially increases the steam generating capacity of each unit, while eliminating any danger of local overheating of the tube banks.

While in accordance with the provisions of the statutes I have illustrated and describedherein the best forms of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus without departing from the spirit of the invention covered by my claims, and that certain features of my invention. may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. Fluid heating apparatus comprising a furnace, fuel burning means in u said furnace, a bank of fluid heating tubes, arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies relative to the front of said tube bank, said tube bank having substantially all of said furnace being, parallel and similarly positioned throughout their the tubes in the row nearest nace, fuel burning means in said furnace, a bank.

of fluid heating tubes arrangedfor a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of said. tube bank, said tube bank having substantially all of the tubes in the row nearest said furnace being parallel and similarly positioned throughout their lengths relative to the longitudinal center line of said furnace and the gas flow areas between the tubes of said bank relatively proportioned to provide a variation in gas flow area longitudinally of said bank effecting a substantially uniform convec-- spacing the tubes of the banks in' accordance the disadvantages another portion of the nace, fuel burning means in said furnace, a bank of fluid heating tubes arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of said tube bank, said tube bank having substantiallyall of the tubes in the row nearest and similarly positioned throughout their lengths relative to the longitudinal center line of said furnace and the gas flow areas between the tubes of said bank relatively proportioned to provide a relatively small flow area through the longitudinal portion of the bank in position to receive heating gases having a high velocity of approach and a larger flow area through the longitudinal portion of the bank in position to receive heating gases having a lower velocity of approach to thereby etfect a substantially uniform convection heating of the tubes in the same longitudinal row of said tube bank.

4. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a bank of fluid heating tubes arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of the tubes in said tube tank, said tube tank having the gas flow areas between the tubes relatively proportioned to provide a relatively small flow area through the portion of the tube length in position to receive heating gases having a high velocity of approach and a larger flow area through the portion of the tube length in position to receive heating gases having a lower velocity of approach to thereby effect a substantially uniform heating of corresponding tubes in said tube bank throughout their lengths.

5. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a bank of fluid heating tubes arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of said tube bank, said tube bank having the diameters of the tubes in difierent longitudinal portions of said bank relatively proportioned to provide a relatively small gas flow area through the longitudinal portion of the bank in position to receive heating gases having approach and a larger gas flow area through the longitudinal portion of the bank in position to receive heating gases having a lower velocity of approach.

6. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a bank of fluid heating tubes arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of said tube bank, said tube bank having substantially all of the tubes in the row nearest said furnace being parallel and similarly positioned throughout their lengths relative to the longitudinal center line of said furnace of the tubes in difierent longiof said bank relatively proportioned to provide a relatively small gas flow area through the longitudinal portion of the bank in position to receive heating gases having a high said furnace being parallel velocity of approach and a larger gas flow area through the longitudinal portion of the bank in position to receive heating gases having a lower velocity of approach. 7. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, at bank of fluid heating tube arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of ap proach of the heating gases in said furnace varies along the length of said tube bank, said tube bank having the diameters and spacing of the tubes in diiferent longitudinal portions of said bank relatively proportioned to provide a relatively small gas flow area through the longitudinal portion of the heating gases having a high velocity of approach and a larger gas flow area through the longitudinal portion of the bank in position to receive heating gases having a lower velocity of approach to thereby effect a substantially uniform convection heating of corresponding tubes in said tube bank.

8. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a bank of fluid heating tubes arranged for a heating gas flow from said furnace-transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of said tube bank, said tube bank having tubes in different longitudinal portions of said bank provided with projections thereon extending into and obstructing the intertube spaces, said projections being proportioned relative to the associated intertube spaces to provide a relatively small approach and a larger gas flow area through the longitudinal portion of the bank in position to receive heating gases having a lower velocity of approach to thereby effect a substantially uniform convection heating of corresponding tubes in said tube bank.

9. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a pair of oppositely inclined banks of fluid heating tubes at opposite sides of said furnace, each of said tube banks being arranged for a heating gas flow from said furnace transversely of the tubes therein and so. arranged relative to said furnace that the velocity of approach of the heating gases in said furnace varies along the length of said tube banks, each of said tube banks having substantially all of the tubes in the row nearest said furnace being parallel said tube banks.

10. Fluid heating apparatus comprising a furnace, fuel burning means in said furnace, a pair bank in position to receive of oppositely inclined banks of fluid heating tubes at opposite sides of said furnace, each of said tube banks being arranged for a heating gas flow from said furnace transversely of the tubes therein and so arranged relative to said furnace and fuel burning means that the velocity of approach of the heating gases in said furnace varies along the length of the tubes in each of said tube banks, each of said tube banks having the gas flow areas between the tubes in different portions along the length of the tubes of said bank relatively proportioned to provide a relatively small flow area through the portionof each bank in position to receive heating gases having a high velocity of approach and a larger flow area through the portion of each bank in position to receive heating gases having a lower velocity of approach to thereby effect a substantially uniform convection heating of the tubes in each of said tube banks substantially throughout their length.

11. Fluid heating apparatus comprising a fur-- nace, fuel burning. means at one end of said furnace, a pair of oppositely inclined banks of fluid heating tubes at opposite sides of said furnace, each of said tube banks being arranged for a heating gas flow from said furnace transversely of the tubes therein, each of said tube banks having substantially all of the tubes in the row nearest said furnace being parallel and similarly positioned throughout their lengths relative to the longitudinal center line of said furnace and the gas flow areas between the tubes in difierent longitudinal portions of said bank relatively proportioned to provide a relatively small flow area through one longitudinal portion of each bank and a larger flow area through another longitudinal portion of each bank to thereby effect a substantially uniform heating of'similarly positioned tubes in each tube bank.

12. Fluid heating apparatus comprising a furnace, a pair of oppositely inclined banks oi fluid heating tubes at opposite sides of said furnace,

each of said tube banks being arranged fora heating gas flow transversely of the tubes therein, fluid fuel burners below one of said tube banks and arranged to discharge towards the opposite tube bank so that the velocity of approach of the heating gases in said furnace varies along the length of the tubes in said opposite tube bank, said opposite tube bank having the gas flow areas between the tubes in difierent portions of said bank relatively proportioned to provide a relatively small flow area through the portion of said bank in position to receive heating gases having a high velocity of approach and a larger flow area through-the portion of said bank in" position to receive heating gases velocity of approach to thereby effect a substantially uniform distribution of the heating gases between said tube banks.

EEWIN G. BAILEY.

having a lower