US2604885A

US2604885A - Multiple tube direct fired air-heating furnace with crown sheet cooling means

Info

Publication number: US2604885A
Application number: US133349A
Authority: US
Inventors: Carlyle M Ashley
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1949-12-16
Filing date: 1949-12-16
Publication date: 1952-07-29
Anticipated expiration: 1969-07-29

Description

July 29, 1952 c. M. ASHLEY MULTIPLE TUBE DIRECT FIRED AIR-HEATING FURNACE WITH CROWN SHEET COOLING MEANS 2 SHEETSSHEET 1 Filed Dec. 16, .1949

INVENTOR.

July 29, 1952 MULTIPLE TUBE DIRECT FIRED AIR-HEATING FURNACE WITH CROWN SHEET COOLING MEANS 2 SHEETS-SHEET 2 Filed Dec. 16, 1949 FIG.4

INVENTOR.

Patented July 29, 1952 ICOQITIINGMEANS lratio ri oi Delawarei This'invention: relates to ."dimaestimates and more particularlyuto .a gas' fired-iunit heater includingsbafile members .to cool theicrown sheet thereby permitting increased .1.capacityof the unit. -I V 'In' gas "fired unit heaters 'Ia' l'majorr: problemz-residesiinr'the manner .in which thericrown sheet is hooked. The crown sheet :comprisesthe .horizontallsectionzof' the :combustion' chamber looking directlyido'wn "upon. the; :burnen h'ead so :that it 110 r Figures is 'an' enlarged -viewvin 1aaaaaamt,

..i extremely. difficult to cool. satisfactorily. The temperature :13f the :area 7 formed; hy.:thecrown sheet -:becomes a limiting,:factor=in.-:the: design of: the; gas fired theater with; regard "to capacity since; this temperaturel-mustr be slimited', to; a certain maximum." Ordinarily, stair. sis --blown straight through the passages-:betweenthetubes and ;across the V crown :sheet:,:-=By gtherztime, the rain has reached the-discharge :side:;ofthe.- unit,

.ittzhas; gained sufficientxheat by earlier contact to provide a :direct :fired heater. in ,which means lare-gprovided to cool satisfactorily the [crown sheetthereby ,permittingan increase in the ca- .pacity; of then-nit. t An gobj'ect of the; present invention is ;-to pro- .vide a direct fired heater containingsbafiies which eontinuously direct successive streams. of fresh air; against the crown 'sheet .to (cool. the: same. A;f-urth'er gobjectis to provide a 1 baffle arrangement for avdirect firediheater whichsegregates portions of fresh or cool air as they are delivered from the fan at the rear of the unit and carries this .cool air forward. andldownlthrough the heat, exchanger before delivering it still un- Iheatedby any contact with the interchanger suriace against the crownsheet at the forward or.

" discharge side of the unit. Further objects ofmy inventionwill be readily perceived from'the folv lowing description.

'fIhi's' invention relates to adirect fired heater cornp f ing' a .icasing containing a'h'eating unit,

a; fan o direct air "through the'heat exchanger "ofthe' unitand a motor'to operatethe' fan. The

unitincl-ude's a combustion'chamber having a crown'sheet, a heat exchanger-connectedto the combustion chamber comprising aplurality of l 'tionsof air drawn'by'thefan within the casing f Carlyle M sAshleyfFayettevillcg..Ni:YJassighor to 1 I v Carrier Corporation, :Syra-cuse; -N.:-Y.-; ;a omev against the upp'ercsu cool the same:

struction of the heating-tmit; t r

*Fie'u' e ZEis a 'front ielevationw-tof the heater "shown Figureiil;

"illustrating th'e baffie arrangementof the' present Rferring -toi the:drawi-ngsthere..is-:disclcsed a gas' -fired unitiheater': including a casing- 2 containing a heaterfiunitwt. Heating unite-com- -prises a gas' burner :4, t a combustion: chamber- "having a: crown..=sheet' '6;:and- .a heat exchanger dis'posed: abOvewombusti'on" chamer. 1 Heat exchanger I comprisesiaiplurality of spacedtubes 8 ex=tendirrgupward from "and connectedtacombustionch'amber" :515Tuhes 8 form air'passages' 1 9 lth'erebetween. rfan ml 0 is provided actuated 'byf-a motorsililu to tforce airl through pass-ages 9 t'ci he'at the samefby :placing' them-in heat exchange relation=1with the heatedgases in tubes 7 8. These areicharacteristic elements et '1 ai gas fired he'ating'unit :and consequently :dq not 15e- "quire -extended :idescriptionr In 'such gas fi'red heating -nnit,- -f-an; l ll blQVS the air through the heat exchanger between the tubes and acr'ossrithe. crown sheet, Air passing over thess'crown .Lsheet is. heated byearly con- 'tact in the entering side of :theunitso thatdur- 7 ing it's passagethrongh the"'unit,- .in-eitect .a 1 temperaturegradient exists. f romthe; crown sheet 'to-a-ipoint in thexairrstream: whereby not only is the temperatureof the air raisedjbut: the rate of 40 heat transfer from :the :crown sheet-is decreased "-By lthe timeissuc'h air has reached; the: discharge side bfithesunit its coolingclcapacityis considerably: less than whenhit begandtsgpasSage through :the unit. Consequently; a the {crown sheet is, not

,45:icooled.to-a-desiredextentsozthat it limits the designvof: theunit withtregard-rtol capacity, I have foundith'at ifxfresh .;or 1 unheated portions ;of air are continuously brought into contact-with the crownflsheet; anjextremely high rate -.-of ;heat

lw transfer.rcanube obtained since suchtemperature gradient is eliminated permitting a substantial increase in the cooling effect of the air stream *upon the crown sheet. To direct-fresh or unheated portions of the air stream into contact Bl'with I the. crown i sheet; I provide a plurality ;of

uface rahiei wn:shetitb rnea maating mama separated be provided with 2.

baflie members 12 disposed in the passages between tubes 8. Bailles 12 are spaced from tubes 8 and crown sheet 6.

Each baiile member I2 is formed of a single metal sheet bent to form side walls 13 of triangular contour. The adjacent side M of the triangle (the lower edge of baflle i2) is placed in proximity to crown sheet 6. The opposite side of the triangle IS (the right-hand side of the baille as shown in Figure 1) is placed adjacent the in: let of heat exchanger '1. The sidewalls l3 form an opening l6 at the opposite side of the triangle through which air enters chamber 11 formed by side walls l3. Opening 06 is approximately the height of bafiie l2. An opening [8 is-providedin the bottom of bafiie l2 adjacent crown sheet 6 and extends substantially the length-of baflie I afdi'rect" fired heater the combination of a casing having an inlet and an outlet, a burner, a combustion chamber having a crown sheet, a

heat exchanger connected to the combustion chamber comprising a plurality of spaced tubes extending therefrom in the casing between the l2. Baiiie I2 occupies approximately one-half l of the width of the air passage between-lads i=2 jacent tubes 8. WhileI have described baflles l2 as'being of triangular contour for ,ease of manufacture, it will be understood the bafflles may be of any desired geometrical contour provided theinterior surface .is designed todirect unheated portions of the air stream continuously against the crown sheet.

Bafiles 12 are mounted. by means of; clips lfi upon metal bars and 2i. BarsZOaHdU-fi welded to clips 19 adjacent opening Hi. he baffie assembly formed by. bars 20 and 2 L and bafiles l2 maybe disposed in placein the airpassagesfi by

tack welding bars

20 and 2| to tubes 8164; each side of unit 3.

In many cases fin members Hare-disposed in air passages 9 to increase the amount of heat exchange surface thus aiding in cooling crownsheet B. Fins 22 preferably are shaped to provide a greater area of heat exchange surface at the outlet of the unit as shown in Figure l. Pins 22 may be provided with an upper edge which extends;

diagonally upward from the inlet edge of the. fin to the outlet edge of the fin thus considerably increasing the area of fin surface atthe outlet and assuring that fresh portions ofairare brought into contact with In such types of construction each bafiie 1 2 may slot 23 extending along the hypotenuse of the triangle through which fin 22 may extend when baffle 12 is in place in air passage 9. The fins 22 and bafiies l2 cooperate'to increase the cooling capacity of the air stream with regard to the crown sheet.

Fan it! forces air within chamber H of baffle I2, such air being deflected downward-and forward in the bafiie until it is forced against the crown sheet 6. The air then passes through the spaces between the side walls l3 of baflie I2 and the crown sheet and moves forward to discharge side of the unit. In effect, portions of the entering air stream in successive streams are'forced.

down to contact the crown sheet 6 at which point such air escapes from baffle l2 and moves up diagonally along the walls of thepassage 9 thereby providing a positive flow of continuously fresh portions of air to-the crown sheet to cool the same effectively. By continuously bringingunheated portions of the air stream in direct contact with the crown sheet, a preheated layer ofairisnot present permitting a far higher convective. conductance. placed from the crown sheet by a new portion of air. v.

The present invention provides a gas fired unit heater having its capacity greatly increased at low cost. The limiting. factor in design of a'gasg;

the fin throughout its lengths-w The air is being continuously: dis--' inlet and the outlet, a fan for moving an air stream through the passages between the tubes, and a baffle to direct unheated portions of the :air stream delivered by the fan within the casing against'the uppersurface of the crown sheet to cool. the same, said baflie having a bafliing surface disposed in spaced, inclined relation with respect to the crown sheet with its end adjacent the inlet being disposed at a greater distance froin .the crown sheet than its end adjacent the Outletfsaid bafiie comprising a member having triangular side walls, a top wall connecting. the sidewalls and an opening at the inlet side of the heat i exchanger. extending substantially the f height-of the triangularv side walls, a second opening at the base of the member adjacent the crown sheet extending substantially the length thereof.

the top 'wall deflecting substantially unheated portions of the air stream against the upper surface of the crown sheet.

Y 2. In a gas fired heater, the combination of a in the casing, a combustion chamber having a crown sheet, a heat exchanger connected to the combustion chamber comprising a plurality of spaced elements extendin therefrom in the casing between the inlet and the outlet, a. fan for moving an air stream through the passages between the elements, and a bafiie arrangement disposed between adjacent elements and having a bafiiing surface disposed in spaced, inclined relation with respect to the crown sheet with its end adjacent the inlet being disposed at a greater distance from the crown sheet than its end adjacent the outletto continuously direct fresh portions of the air stream passing through the heat exchanger against the upper surface of the crown sheet;

3. A heater according to claim 2, in which the baffle arrangementincludes spaced bar members extending across the rear of the heat exchanger crown sheet to cool the same, each baffle member being disposed between adjacent elements and having a bafliing surface disposed in spaced, inclinedrelation with respect to the crown sheet with its end adjacent the inlet being disposed at a greater distance from the crown sheet than its end adjacentthe outlet.

4. A heater according to claim 3 in which each bafiie member is spaced from the crown sheet. 5. In a gas fired-heater, the combination of a casing having an inlet and an outlet, a gas burner in the casing, a combustionchamber. having a between the inlet and the outlet, a fan for forcing an air stream through the passages between the tubes and a plurality of baffles disposed between adjacent tubes, each baifie having a bafiling surface disposed in spaced, inclined relation with respect to the crown sheet with its end adjacent the inlet being disposed at a greater distance from the crown sheet than its end adjacent the outlet, each bafile comprising a triangular memher having side walls, a top wall connecting the side walls and an opening at the inlet of the heat exchanger, the base of the'triangle being placed in proximity to the crown sheet.

6. In a gas fired heater, the combination of a casing having an inlet and an outlet, a gas burner, a combustion chamber having a crown sheet, a heat exchanger connected to the combustion chamber comprisin a plurality of spaced tubes extending therefrom in the casing between the inlet and the outlet, a. fan for forcing an air stream between the passages between the tubes and a plurality of baffles disposed between adjacent tubes, each baffle having a bafiiing surface disposed in spaced, inclined relation with respect to the crown sheet with its end adjacent the inlet being disposed at a greater distance from the crown sheet than its end adjacent the outlet, each bafile comprising a member having triangular side walls, a top wall connecting the side walls and an opening at the inlet side of the heat exchanger extending substantially the height of the triangular side walls and a second opening at the lower side of the triangle formed by the side walls and the top walls in proximity to the crown sheet extending substantially the length of the triangle whereby successive portions of the air stream passing through the heat exchanger are forced which fins are disposed between adjacent tubes, said fins extending through openings in the baffies.

' 9. A gas fired heater according to claim 8 in which the edges of the fins extend upward from the inlet edges of the fins to the outlet edges of the fins thereby increasing the areas of the fins throughout the length thereof.

10. In a gas fired heater, the combination of a casing having an inlet and an outlet, a gas burner in the casing, a combustion chamber having a crown sheet, a heat exchanger connected to the combustion chamber comprising a plurality of spaced tubes extending therefrom in the casing between the inlet and the outlet, a fan for forcing an air stream through the passages between the tubes, triangular baifie members disposed in said passages to deflect fresh portions of theair stream passing through the passages against the upper surface of the crown sheet to cool the same, each baiile having a baffling surface disposed in spaced, inclined relation with respect to the crown sheet with its end adjacent the inlet being dis posed at a greater distance from the crown sheet than its end adjacent the outlet, each triangular member being formed from a single sheet bent to form side walls and a top wall connecting the side walls to receive air at the inlet side of the heat exchanger and to deflect such air downward against the crown sheet.

11. A gas fired heater according to claim 10 in which a baiiie member occupies approximately one-half of the widthof the air passage between adjacent tubes.

CARLYLE M. ASHLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,958,331 Bell May 8, 1934 2,129,059 Herbster Sept. 6, 1938 2,194,733 Andersen Mar. 26, 1940 2,289,759 Denise 'July 14, 1942 FOREIGN PATENTS Number Country Date 362,630 Great Britain Dec. 10, 1931