US1690326A - Air heater - Google Patents

Air heater Download PDF


Publication number
US1690326A US124957A US12495726A US1690326A US 1690326 A US1690326 A US 1690326A US 124957 A US124957 A US 124957A US 12495726 A US12495726 A US 12495726A US 1690326 A US1690326 A US 1690326A
United States
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John E Bolling
Szekely Ernest
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Drying Systems Inc
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    • F28D9/00Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall


Nov. 6, 1928. T 1,690,326.
J. E. BOLLlNG ET AL AIR HEATER Filed July 26. 1926 4 Sheets-Sheet 1 J. E. BOLLING ET AL AIR HEATER 4 Sheets-Sheet lllllllllll v l I v 1 l l l l l l l l V I A I I l l I 1 I 1 l n I I l I u! Filed July 2's, 192s (lags Q E fizveizz'ws. FJohn E Bolln' 772 as? jzeiie Nov. 6, 192a 1,690,326
AIR HEATER Filed July 26, 1926 4 Sheets-Sheet 4 Patented Nov. 6, 1928.
; UNITED: "sfrnr lasi Assmnonso! THBEEJOUBTHS TODBY .aconronar on or ILLINOIS, ,AND ua-rover To ERNES'LSZEKELYI 1 Arr; HEATER. I
The main objects of this inventionlare to provide a more efiicient fi uid heater particle larly'for =h-ea-ting la1ge quantitiesrof air to high =temperatures to provide a simple, self;
5 contained; economical liglmweight Welded or Iockseamed I sheet metal construct-ion to provide an air heater having true counterfioWbetWeem-the air and the combustion gases to: p'rrovide a more suitable arrange; 1 ment of flues for accelerating the heat interchange to provide aheater having thieycombuetion -tube'and the -fill8 tubGS integrally I joined into a composite-unitwhich iisxthen. freely supported inthe heatericasing to allow movement for thermal. .x.expansiorr and:
contraction; to provide an improved form of combustion tubeadapted to Withstand the high combustion temperatures; to provide means for evenly distributing theiaair to be heated around thegeombustion tll b 'in Order to prevent uneven circulation, and uneven heating'of the tub'e, and Lfor. improving the fuel combustion; to provideawfurnace: in) Whichall of the passages,andsespecially the flue gas passa 'es, are accessibleforxcleanin ;r to providea eater-unit whicli is adaptable to be connected :into battenieawi'ith a saving in the amount of aiiudiwtv piping requiredr and also to reduc'e heat :losses and the amount of space occupied: I V In the prior devices substantiallyv no'aata tenrpt Wasunade toobtain. ll'IlTfOIIIlf evenly distributed airi circulation; xthroughout the: furnace" This reeulted'iin lowvefiiciency. and:- caused portionsofthe furnace ,tObQCOITlGZOIVGF- heated? The overheated spots disturbedthw air circulation and causedthe destruction of the "furnace imeltingndowni the adj oinlnig metalwallsf: i
In this invention :the outer: shell or:-enWeilopeds rectangular indormeand is bu'ilt up; 035- panels of iheat resistingimaterial i encased? in sheet 1 metal. The combustion. chamber and fine gas structures are: suspended sin the 1 envelope withi freedmnr to movemndertex- 3 pansion; The combustion chamberiis encyl- 1 inelrieal sheetnnetal tube {provided with 10mm gitudinal fins on the: outsid,:.and is enclosed by a'larger tube which fOImSiUJRifOIYHI periph i eral 1 airspacee and serves to confine the: air melamine; cliosely to the-:waHs'aotthe i COIn-i 1923i Serial No.- 124,957"
bustionz tube. The gas lpassageuduets: are: joined'to 'thierear enzd the comhustionitubee eliminating the customary flue sheetsg-Thc" gas fines comprise apairzofipara'llel fiatlduacts Whichextend forwardlycover thentop ,Oifithel combustion tube, and then; upwardlya and back to the. rear endofitlre outer envelope;
Where theyareszconnected zinto d to'ithe stack. .o Transverse bafiie'sheets are provided under: the lower pair of ductsan-dbetweenthelupper: and lower pairs. The jbafflesdirecti theeain which 7 enters at i the upper? rear ends of; the 1 i furnace, forwardly: around iandizbetweenxithe? upper pair of: ducts',1-.then%: -cl0wn and; rear- Wardly in! contact-1 with their lower gairaof ducts, and again down sand =t-lienlforwardlyv through the baflled space around the comhuse tion tube. 7 The .gas ducts areirectanguilar; in; 7'} cross section, considerably:-greater"inwidtlr thanziin thickness, andnthespace :aroun'drthe" ducts is uniform and quiteenarrow sorthat. the aim isz also; confined; close atoatheasurface OfIt-hfi ducts. 1 i t The discharge ends-ofthe gas lducts are; reduced in Width because the flue {guisesv are: cooled. and i reduced in i-volume: by-theeentoer ingyair; Also vertical bafileepl'ateshre; pr0- uctsrleadiilgi' r (in VllClCli atzthe sides 20f zthe-*- reduced-iends; which so extend parallel to the converging 'sidessof the upper rlticts, and then flare outwardly totem;
a Venturi i'constrictionif()1111dl.lfll ng rtheresist. V i
anee to the incoming-air; "Dim flaring ends; also provide a'small expansion:,chamberriforg the entering airxin: which the-velocity: isi reduced z andi-the "pressure equalized; to evenlyv distribute the air: in enterin around the gas-ducts. T r The =crossr sectional areaxis v increasedjas the; air isrheated aim-flowing along-the upperipairof ducts to lessen"?itheivelocityaearlongi theflew coolert portions :of the :ductslin proportion to the slower rate of heat l interclmnge Atsthez' forward lend. of :the upperaductstherair flows 95 down i and i back along .& the. surfaces {of 1 sthe lower pair, andithencclown into aasecondiiem largecltchambevatcthe rear of; the ieombu-s-ition tu'bbwvhichacauses-gthe agiirito-bedistribu tw ed evenly around the combustionvtubes; 10 Theaspace around the alowervp'air OitdtIGiJS": is. held substantiallyalmifonmu a The stair-1 pen t-inues to expand and consequently increases in velocity in approximate proportion to the increase in the rate of heat interchanged along the hotter portions of the lower. ducts. This arrangement accordingly increases the cooling of the lower ducts and maintains the upper and lower reaches more nearly at the same temperature and prevents overheating in the lower portions, which are adjacent to the extremely high temperatures in the combustion tube.
The cross seetiona area around the combustion tube is notgreatly increased and consequently the expansion from the combustion temperatures causes the air to flow at very high velocities. This prevents the combustion tube from being melted.
The battle [ins in the space between the combustion tube and the enclosing tube prevent the air from the lower side from rising to the upper side: and maintains a more equal distribution. Since the air is confined to longitudinal passages along the tube. the higher temperature at the upper side causes greater velocities and results in an inert in the amount of cooling. Consequently the tem peratures of the upper and lower portions of the tube are nearly equalized.
By more correctly proportioning the differeut parts of: the furnace, as described. the el'liciency of the heater unit is greatly increased. The maximum air flow and high est rates of combustion may be attained. The walls may be heated to the maximum sate temperature throughout and destructive temperatures prevented.
The construction of the heater unit is such that the heated air may be conducted out through the top of the outer shell or out through either side. The trout end at the furnace is suitably apertured at the top and sides to receive fittings which may be closures or which may provide apertures for receiving the ends of the comnuinical ng ducts. as may he desired. This permits stamlardizing a single type of heater unit which is adaptable to be used interchangeably in nearly all classes of installations.
The apertures at the sides are also adapted for receiving short rectangular tubes for connecting the units in batteries and drawing the heated air out through a single duct at one end. This reduces the overhead space required and effects a large economy in the amount of necessary piping.
In this invention, the con'ibustion chamber, which is a sheet metal. tube disposed in a horizontal plane and the combustion gas fines are joined into an integral construction which is flexibly sustained in the heater casing with the combustion tube extending loosely through the casing and slidably fitted in the casing opening. The oil burner nozzle mounted in the open end of the combustion tube, and the terminus of the flue tubes e:-:-
nceasee tends slidahly through the end wall of the casing, so that the structure forming the combustion gas passages is continuout-a. The entire outer surface of the metal walls in contact. with the burning gas is exposed to the circulating air and is available for useful heat transmissitm. Leakage is avoided. vertical line sheets are eliminated, and cracking or breaking at the joints avoided l allowing freedom for the thermal volumetric changes in the metal.
Also, the greater part of the heat intcr change is caused to take place around the combustion tube, which is made ol a chrome steel alloy which especially capableol'withstanding the high temperatures. The tube is built it of segmental marginally flanged strips welded together in a suitable manner. The combustion tube extends through a tube in the casing which bears on the outer edges ol the flanges.
An illustrative embodiment of this invention is shown in the accompanying drawings, in which:
Figure l is a perspective view of the heater with parts broken away and with the casing shown in broken lines.
Fig. 2 is a vertical section on the longitudinal axis of Fig. 1.
Fig. 3 is a section taken on the line 3 3 of Fig.
Fig. -l is taken on the line ll of Fig.
Fig. 5 is a front elevation of the heater with a portion broken away.
Fig. 0 is a section on the line --G of Fig. 3. Fig. 7 is a fragmentary detail of one end of the combustion tube.
Fig. 8 is a iragu'iental plan view of a battery of heaters.
Fig. 9 is taken on line 9 4) of Fig. 8.
Fig. 10 is a pers-ipeetivc view ol' the front end ol the heater casin Figs. 1]., l2. l3, l4; and l5 show dill'erenl types ot fittings tor the trout end of the cusing shown in Fig. 10.
Referring to the drawings. the shell or envelope 1 of the heater is preferably built up of insulating walls comprising a thickness of non-eomlueting material '3 encased between the sheet metal walls 3. ln arrangement. the outer shell 1 comprises a long rectangular chan'iber 41. rounded at the. bottom. and a narrower rectangular chamber 5 in front of the chamber i and connecting therewith through the circular opening An air inlet port 6 is provided at the rear at the upper wall of the casing, and the air is drawn out or forced out through an upper opening 7 in the chamber 5, or through side openings 8 when the heaters are arranged side by side. A baille plate or horizontal partition 9 extends from the dividing wall between the chambers l and 5 above the opening 5, toward the rear of the casing, and the second battle plate 10 located above the ballle 9, and extends from but ill:
the remrrwal] zofmllic casingy,;iorwfardly. An
iorwardly above thel upp'eriba e 10,wcircu1at ing around and upper 'fi-ue tubes,-
downwardly between the fonward endofthe baflie 10, rearward'l throughithe space he tween tlie upper an flower halite plates; then a horizontally disposed 1 combustion or. firing tubef12, and the :fluerducts- 13 which form a a continuationof the' combustion tube 12, and are doubled l back over the combustion: tube between tlre baflle plates 9zand :10, and then extend arearwardly: above the upper baffle 10 to thc' -sta'ek outlet 14, at thetrearTof'i the casingi The flue tubes 1'31'are of a H at rectangu' lar construction arranged 1- and connected. to form double channels with I spaces between the tubes.- Atrthe rear end, the upper-flue: tubes arereduced in width so that the airscan circulate between the Itwo upper tubes, and so that the area of the flue passes is reduced approximately: inmaccordanee with the w'diminshing volume of the cooling gases. This reduction in flue areaialfords a two:-fold advantage. It. insures a uniformly high rat-e ofztranlsmission and renders it difiiicult to burn an excess quantity of fuel.
Theoil burner nozzle is mounted in a casting lti which is'support'ed within the tube 16 which is billed F to: the front end 1 of i the combustion tu e l2gas shown infig.2. Oilis sprayed fronrthe-nozzle lfilidirectly into the tube-Hand the combustion takes place along the length or "the tube at very. high tempera-- tar-es.
Th e air enters tl flrough the rt 6, passes downwardly 'and forwardly around the pe-: ripheryof the combustion tube 12 and then leaves the casing from the chamber 5;. T1181 outer end f or terminus 16 "of'the flfue tubes is slidably supported, and the weight ofithe' bank of fines is flexibl I suspended from the to wall- 0f the casing l by means of suitable supports 17. "The combustion tube is provided with outerv longitudinal ribs or flanges 18 which form a plurality of narrow passages in the space between the tube 12 and the enclosing tube 11. The baflies or flanges 18 thereby evenly distribute the flow of air around the heated tube 12 and prevent Stratification or uneven circulation.
The tube 12 is built up of channel shaped strips 19 having the outwardly extending fianges.18.. The abutting flanges are welded in a line along the length of the tube, preferably near'the bottom of the flanges. Since the flanges or ribs are integral with the wall of the tube 12, the heat transmission is much greater than is obtainable with non-integral extended surfaces. 1
The sides of the upper pair ofgas ducts 13 are tapered inwardly as shown in Fig. 3 and vertical baflie walls 31 are provided at the: sides wof therzu'pper ducts,' between 5 the the shell l. The waillsBlrextnd parallelto the sides not the ducts and then flare: outwardly at the; rearcend to formthe'venturi upperwho'rizontal: plate 10.:and the :top of 1 restriction: 32 and the expansion chamber "33." Inthisconstruction all parts oft-he heater are: readily accessible for" inspection and" cleaning. The stackmay-be disconnectedsat 14-to1a=fford access to the upperlayer :of fines; The lower fines are accessible through a port in the rear: end 0f the furnace, which :is: hermallyuclosed' by. thescover 21,- and the chants her 5 may closures. a
When the heaters are :installed side by. si de in a batteryformation, it isespeci-all'y desirreached by removing the side:
able to be able to remove any onerof the-units without disturbing the remaining units. Accordingly, recesses 22 areztorm'ed lnmthe side of 'thei'ro'nt end of the outer shell 1. i The recesses are open at the front and! at: the
top, and the short rectangularconnecting tubes 23 may be inserted after the units-are V in place. The tubes 23'are =then secured i-by with the front wall of the units Iat' the lower end and extend I over the: front and: across: the top where the straps =24c|are securedbythe bolts-25. Preferably the straps are*wider than the connecting-tubes123 and: coverrt hei joints between the tubes and the adjoining neans oi the'flat stra-pss24, whiclrxengage 7 units; W hen'dt is =desired tosremove a cer-- tain unit the straps are loosened and the con! necting tubes 23 withdrawn; Then the :unit" maybe removed forwardly without disturb I ingthe' remaining units.
' When it is desired to entirely close: the side, as -a-t the--right" side' of" Figure 8, aziplane' insula'tingpanel 25 isinserted in the 'recess 22 and held in -place by" an angular strap -26.
Aside' outlet is shown at the-lettisideiof Fig. 8;; The tube 27 is insertedin a suitable orificed side-panel 28, which is secured Ein the recess 22-:or'the end unit in the rsanaerna-annerl thatitherclosnre 25wissseeured. The outlet tube 27 may also be used in the top outlet aperture 7, or the aperture 7 may be closed by the cover 29. The cover member 29 is con- V structed with a flange 30, which is adapted to project under the edges of the closure strap 23 or 26, as the case may be.
which may be assembled in any suitable man ner to suit the requirements of the particular installation. i
In operation, the air iscontinuously circulated through the casing around the fines in- .true counter-flow relation to the heated gases,
maximum temperature of. the tube may be In this manner 7; one standardized feature unlt 1s provided maintained without burning the tube in spots. \Vhen the tube is raised to a red heat or a white heat, although the metal is not destroyed, there is a tendency for sagging; since the metal becomes weaker. By proiiding' the longitudinal flanges, the walls of the tube are well supported and the useful lite ot the tube is lengthened. The flanges also materially increase the radiating surface, especially where the flanges are integral with the tube walls, as shown.
\Vhile but one specific embodin'ient of this invention has been herein shown and described, it. is to be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention, as defined by the following claims.
e claim:
1. In an air heater. a combustion tube for burning fuel. said tube com n'isinn' a plurality of longitudinal segmental strips having: mar ginal flanges projecting" outwardly, said strips joined at the edges.
2. In an air heater, a casino, an air tube mounted in said casino, a combustion tube having a plurality of longitudinal outwardly projecting ridges, said comlmstion tube being supported in the air tube by said llflfJOS and unrestrained for longitudinal thermal expansion and contraction.
3. In an air heater, a casing having, an upper outlet. a combustion chamber in the lower part of the casing, flat. flue tubes extending back over the top of the combustion chamber and then forwardly at the top of the casing to said outlet, said flue tubes forming a continuous passage from the combustion chamber to said outlet, said casing having an air inlet near said outlet, and baffles across the chamber for directing the air.
-l. In a. fluid heater a. combustion tube, horizontally flat flue tubes arranged in reversel extending layers above the combustion tube and forming: a. continuous passage therefrom, means for oppositely directing the fluid along;
the successive layers of the tubes and then along the combustion tube.
In a fluid heater. a casing, a. horizontal combustion tube, flue tubes arranged in reverscly extending layers above. the combustion tube and forming a continuous combustion gas passage therefrom, said combustion tube and flue tubes beina integrally connected, means for snspernling the flue tubes in the casing and a support for the con'itnistion tube.
6. In a fluid heater, an outer envelope of heat insulating material having ports and battles for directing the fluid to be heated through the heater. a sheet metal firing tube, and continuous sheet metal combustion gas ducts 'toloed back and forth in layers above the firing: tube and joined thereto to form an integral structure. said :-:tru .:ture fleaibl supported in the envelope for heating: the fluid.
7. In combination. a plurality of heater units each llttVilli' apertures in the adjacent sides, and having! flanges around two adjacent sides of said apertures, the units being arranged so that the relatively adjacent flange are in abutment, tubes remorably inserted in the recesses formed by the abutting flan l'es. and a strap attached to the heater units for covering: the joints and holding the tubes in place. said straps extending over the two edges of the tubes opposite to the flanges.
5%. In combination in an air heater a shell haying; an aperture, and having: flanges around two adjacent sides of, the aperture. :1 panel inserted in the recess formed by the flanges for closing the aperture, and an angular section strap extending over the two edges of the panel opposite the flanges and covering the joints between the panel and the shell. the strap being secured to the shell for bold in g said panel.
Signed at Chicago this 94th day of June, 19:26.
US124957A 1926-07-26 1926-07-26 Air heater Expired - Lifetime US1690326A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2457513A (en) * 1943-02-26 1948-12-28 Stewart Warner Corp Internal-combustion hot-air heater
US2538446A (en) * 1944-04-04 1951-01-16 Australian Iron & Steel Ltd Recuperator means for combustion furnaces
US2646263A (en) * 1949-12-27 1953-07-21 Modern Equipment Co Smoke and spark arrester for cupolas
US2749110A (en) * 1952-12-02 1956-06-05 Hartwig Walter Recuperator
US2856915A (en) * 1954-02-16 1958-10-21 Earl F Fromme Forced air heater

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2457513A (en) * 1943-02-26 1948-12-28 Stewart Warner Corp Internal-combustion hot-air heater
US2538446A (en) * 1944-04-04 1951-01-16 Australian Iron & Steel Ltd Recuperator means for combustion furnaces
US2646263A (en) * 1949-12-27 1953-07-21 Modern Equipment Co Smoke and spark arrester for cupolas
US2749110A (en) * 1952-12-02 1956-06-05 Hartwig Walter Recuperator
US2856915A (en) * 1954-02-16 1958-10-21 Earl F Fromme Forced air heater

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