US2825312A

US2825312A - Fluid heaters

Info

Publication number: US2825312A
Application number: US334221A
Authority: US
Inventors: Kolling Johann
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1953-01-30
Filing date: 1953-01-30
Publication date: 1958-03-04
Anticipated expiration: 1975-03-04

Description

2 Sheets-Sheet l mn nzun. DDDDU J. KQLLING FLUID HEATERS March 4, 1958 t Filed Jan. so, 195s.

` INVENTOR v J5/:arm jl/oL//ing d ATTORNEY UDUUD DDEE D man E am .im @fw hun March 4, 1958 A.1. KoLLlNG 2,825,332

FLUID HEATERSA Filed Jan. 5o, 195s 2 sheets-sheet 2 INVENTOR .toward the middle.

United States PatentfO FLUID HEATERS Johann Kolling, Oberhausen, Germany, assignor'toThe Babcock & Wilcox Company, New York, N. Y., a

corporation of New Jersey Application January 30, 1953, Serial No. 334,221

4 Claims. (Cl./122-333) 'Ihe presentv invention relates in general. `to an improved construction of a iiuid heater .having a vertically elongated furnace chamber with fuel burning means in the lower part thereof, and a laterally extending convection heating pass at its upper end;V and, more particularly, to an improved form of gas flow baie means in the furnace chamber subjacent to the convection heating pass in a iuid heater of the character described which are arranged to more uniformly distribute the-heating gases flowing from the furnace across the fluid heating surfaces positioned in the heating pass, and cooperating with a special arrangement of tubes in a tube bankarranged across theentrance to said heating pass.

In Yfluid heaters of the character described, therev is a .tendency for most of the highest temperature heating a slag-forming fuel is burned. This is particularly evident with a furnace chamber having more than four lateral vertical walls which are symmetrically arranged to form a furnace of varying width and depth relative to its transverse center lines'and from which the combustion gases flow laterally out of a gas exit opening whose width yis equal to the maximum width of the furnace chamber. In suchfa case not only the hottest but also the greatest quantity of the combustion gases are pressed This unequal temperature distribution of the gases tends to remain until the gases flow past the last uid heating surface in the convection heating pass. This uneven gas .flow `is particularly undesirable where .vapor superheating tubes are disposed-in the cons n vection heating pass, because localized gas hotfspots tend v Ltoresultintube failure.

. Thejmainobject of my invention is'Y the provision of an improved construction and arrangement of. thefurnace chamber in a fluid heater ofthecharacter .described for controlling the distribution of the heating 'gases .across the width of thevconvection heating pass` by reducing the amountof lhigh temperature gases flowing. through'the `middle portion of the furnace chamber. v

l A more yspecific object is the `provision ofla `furnace nose arch or baffle subjacent.to the -lateral'lconvection :heating pass and, having a middleV portion which` projects Ninwardly. toa greaterextent thaniits side portions, thereby Ycorrespondingly reducing the gas.. owz .area in. the

These gases flow upwardly .at a `greater l ice ,2 distribution across the width 'of vthe'convection heating pass. s

For a better understanding of the invention, itso'pe'r'ating advantages and yspecific objects attained by'its use, vreference should be had tothe 'accompanying' .drawings and descriptive matter in` which I have illustrated and described a preferred embodiment of myfinve'ntion.

Of the drawings:

Fig. vl is a sectional elevation taken on the line 1--1 of Fig. 2 of a steam generating unit constructed in accordance with my invention; and

Fig. 2 isa horizontal cross-section taken'on theli-ne 2-2 of Fig. 1. n y

While in its broader aspects myfinvention is adapted for use in fluid heaters of the general character described,

Vit is particularly designed for-use lin uid heaters having a furnace chamber with more than four vertical side walls. In the steam generating vunit illustrated, for example, the vertically elongated furnace chamber 1 is an equi-lateral Octagon in horizontal cross-section. ln each of the walls 3, 4, 5, 6, 7, 8, 9 and 10 is arranged a fluid fuel burner `2, whose axesv of discharge are symmetrically arranged tangent to an imaginary circle about the furnace chamber axis. These burners arev similarly offset in the corresponding side Walls so that they discharge yin the same angular direction relative to the circle. The furnace walls are lined with steam generating Vtubes throughout their height. The rear walls 7, 8 and 9 and corresponding wall tubes are inclined forwardly and then rearwardly at their upper ends to form a wedge-shaped wall or arch structure 11, which defines a throat 24 adjacent the upper end of the furnace chamber and the inclined bottom 25 of a convection heating pass 26 extending laterally from the Vfurnace chamber `gas outlet 12. The tubes lining the walls 7, 8 and 9 are connected at their upper ends to an intermediate header 14 extending across the bottom of the gas pass 26. The tubes 15 lining the walls 7 and 9 have vertical upper end portions 16 forming corresponding vertical rear -wall sections 'of the throat 24. A vertical screen bank of steam generating tubes .13 extends upwardly from the header 14 to an external transverse steam and water drum 21. A pendant type bank of multiple looped steam super-heater tubes 22 extends uniformly across the gas pass 26 rearwardly of the screen bank 13. The front walls 3, 4 and 5 extend upwardly above the level of the throat 24 and thenat `a rearward inclination to form a furnace roof 27 substantially parallelto the inclined bottom y25 and extending across lthe upper end portion of the tubes 13 .to join the roof 28 of the convection gas pass along the rear side of the drum 21.

- With the described construction and arrangement. the combustionk gases generated in the lower portion of .the furnace chamber ilow lupwardly in the combustion chamber with the greatest quantity, and the hottest, gases concentrating in the middle of the furnace. The resistf ance caused by the walls retard the flow of gases along i special Ynose Vlbaflle .formationin varyingllthefheating gas ywardly through the central portion of the furnace.

the sides of the chamber with the resulting tendency for the gases to take the path of least resistance and ow up- This uneven combustion gas flowand gas temperature distribution tends to continue during the gas flow vlaterally through the convection heating pass 26 'and wouldresult in undesirable heat transfer conditions throughout the convection heating pass. However, in accordance with my invention, a projecting nose arch or baie '17 is provided at the throat section'24, and .this together with an arrangement of tubes in the-tube bank 13provides a t lgreaterresistance to combustion gas owfin thecentral portion of the furnace andconvectionheating'gas.pass, Y Vwhich causes vsome of :the combustiong'ases inlthecen- 3 tral portion of the furnace and convection heating gas pass to flow towards the sides thereof.

The nose arch 17 is formed by a forward projection of the tubes along the rear wall 8 beyond the plane of the tube portions 16 which forms in horizontal crosssection a symmetrical trapezoid, the sides of which are substantially parallel to the front walls 3,`4 and 5." This projecting structure, or nose arch 17, may be constructed `of special tubes in such a way as to allow the gases to pass between the tubes,lor as shown, by covering or lining the tubes withrefractory material, be made in the form of a solid gas directing baffle.

The bank of steam generating tubes 13 is composed of the four tube row groups 18 and 19 adjacent the sides of the convection heating pass and adjacent tubes bent forwardly to various degrees to form a seven tube row group 20 in the central portion of the pass. This arrangement aids in directing the gas flow towards the opposite sides of the heating pass due to the higher resistance to gas flow offered by the seven tube row arrangement inthe central portion compared to the four tube row construction at the sides.

The tube clearance between the superheater tubes transversely to the gas llow direction could also be made closer in the central area of high combustion gas` temperatures. This would increase the gas flow resistance in that area and deflect some of the hotter gases towards t the sides of the heating pass.

Deflecting combustion gases away from the central portion of the `furnace causes an increase in gas flow along the sides of the furnace chamber outlet `and a mixing of the hotter and cooler gases in those areas so that the resultant gas flow through the convection heating pass is more homogeneous. When used in conjunction with the described arrangement of convection heated generating tubes and/or superheatng tubes for providing a greater gas flow resistance in the central portion of the convection heating pass, the heat transfer throughout the heating pass will be more efficient and the danger of tube :failures due to localized hot combustion gases will be minimized;

While in accordance with the provisions of the statutes l have illustrated and described herein the best form of the invention known to me, those skilled in the art will understand that changes may be made in the form of the apparatus withoutdeparting 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.

What is claimed is:

l. A fluid heating unit comprising walls defining a vertically elongated furnace chamber and a laterally extending convection heating pass opening through the rear of said furnace chamber, said walls including opposed substantially vertical front and rear furnace chamber walls, a bank of vertically extending fluid heating tubes positioned in said convection heating pass and extending across the width thereof, means for burning fuel in the lower portion of said furnace chamber and producing a heating gas flow upwardly therein and thence laterally through said convection heating pass, and means for effecting a substantially uniform temperature and transverse distribution of the gases flowing from said furnace chamber into said convection heating pass comprising an arch projecting inwardly from said rear wall and cooperating with said front wall to define a restricted heating gas ow passage opening at its upper end to the furnace chamber space wherein the gas turns into said convection heating pass, said arch having a `central nose portion formed by laterally aligned tubes and projecting inwardly to` a greater extent than its side portions, said arch being spaced from said front wallla distance sutilcient to provide a heating gas ow area in the central porl tion of said gas flow passage `ajlproximating but smaller than the heating gas flow area at the sides thereof `to create a greater resistance to flow in the central portion of said gas passage than at the sides.

2. A fluid heating unit comprising walls defining a vertically elongated furnace chamber and a laterally extending convection heating pass opening through the rear of said furnace chamber, said walls including opposed substantially vertical front and rear furnace chamber walls,` a bank of vertically extending fluid heating tubes positioned in said convection heating pass and extending across the width thereof, means for burning fuel in the lower portion of said furnace chamber and producing a heating gas flow upwardly therein and thence laterally through said convection heating pass, and means for effecting a substantially uniform temperature and transverse distribution of the gases flowing from said furnace chamber into said convection heating pass cornprising an arch projecting inwardly from said rear wall and co-operating with said front wall to define a restricted heating gas flow passage opening at its upper end to the furnace chamber space wherein the gas turns into said convection heating pass, said arch having a central nose portion of trapezoidal formation in horizontal cross-section projecting inwardly to a greater extent than its side portions, said arch being spaced from said front wall a distance sufficient to provide a heating gas flow area in the central portion of said gas flow passage approximating but smaller than the heating gas flow area at the sides thereof to create a greater resistance to flow in the central portion of said gas passage than at the sides.

3. A tiuid heating unit comprising walls defining a vertically elongated furnace chamber and a laterally extending convection heating passopening through the rear of said furnace chamber, said walls including opposed substantially vertical front and rear furnace chamber walls, a bank of vertically extending fluid heating tubes positioned in said convection heatingpass and extending across the width thereof, means for burning fuel in the lower portion of said furnace chamber and producing a heating gas ow upwardly therein and thence laterally through said convection heating pass, and means for effecting a substantially uniform temperature and transverse distribution of the gases flowing from said furnace chamber into said convection heating pass comprising an arch projecting inwardly from said rear wall and cooperating with said front wall to define a restricted heating gas flow passage opening at its upper end to the furnace chamber space wherein the gas turnsv into said convection heating pass, said arch having a central nose portion of trapezoidal formation in horizontal crosssection projecting inwardly to a greater extent than its side portions, said arch `beingsnaced from said front wall a distance sufiicient to provide a heating gas ow area in the central portion of said -gas flow passage approximating rbut smaller thanthe heating gas liow area at the sides thereof to create a greater resistance to flow in the central portion of said gas passage than at the sides, said front wall including vertical portions parallel to sides of the vcentraljnose portion of said arch.

4. A fluid heating unit comprising walls defining a vertically elongated furnace chamber and a laterally extending convection heating pass opening through the rear `of said furnace chamber, said walls including opposed substantially vertical front and rear furnace chamber walls,`a bank'of vertically extending uid heating tubes postionedin said convection heating pass and extending across the widthethereof, some of said tubes extending further toward the; furnace chamber in the center part` of the convection heating pass than those at `the sides thereof, means forburning fuel in the lower portion of said furnace chamber and producing a heating gas flow upwardlytherein and thence laterally through said convection heating pass, and means for effecting a substantially uniformtemperature and transverse distribu-` tion of the gases flowing from said furnace chamber into said convection heating pass comprising an arch projecting inwardly from said rear wall and cooperating with said front Wall to dene a restricted heating gas flow passage opening at its upper end to the furnace chamber space wherein the gas turns into said convection heating pass, said arch having a central nose portion formed by laterally aligned tubes and'projecting inwardly to a greater extent than its side portions, said arch being spaced from said front wall a distance suicient to provide a heating gas ow area in the central portion of said gas ow passage approximating ,but smaller than the heating gas ow area at the sides thereof to create a greater resistance to ow in the central portion of said gas passage than at the sides.

References Cited in the le of this patent UNITED STATES PATENTS