US2196829A - Air heater - Google Patents

Description

April 9, 1940. F. o. Hl-:ss 2,196,829

AIR HEATER Filed March 5', 1938 2 Sheets-Sheet 1 l lNVENTOR Fefaf/e/c 0 #c55 ATTORNEY y 40 space generally like that of the burner rst dewith the burner element of heater partly broken Patented Apr. 9, 1940 'y l I UNITED STATES PATENT OFFICE Am HEATER Frederic 0. Hess, Philadelphia, Pa., allignor to The Selas Company, Philadelphia, Pa., 'a oorporation of Pennsylvania Application Much 5, 193s, senin No. 194,062

ls om (c1. zes-isi The general object of thepresent invention is ing capacity, respectively, which is greater than to provide an improved heater for gaseous fluids, is conveniently` or vpractically obtainablev with a oi the type commonly referred to asan air single unit. The'heaterinlet and outlet are prefheater, and devised and adapted for use in heaterably in alignment so the heater may readily be ing air or other gaseous fluid up to a temperature located directly in a straight pipe or conduit l of 1500 or 1600 F., for industrial or other purline. operatively, my-'improved air heater is poses. characterized by the wide capacity range of an My improved heater comprises a heating space, individual unit and by the fact the heating space through which the nuid to be heated is passed, with its inlet and outlet may be so shaped and having refractory walls and including a burner proportioned. that in moving through the heater.

l chamber in which the burner element of the the fluid heated will surfer only a relatively Small lo heater is mounted, and specially shaped inlet and v105s of preSSl-lre head. S0 that the oost of draft outlet passages communicating through said fan operation may be correspondingly low- When chamber. In the preferred construction, for connecessary or desirable for use in circulating and ditions of use which do not prohibit the admixheating furnace atmosphere eases, the heater ture of the air or other gaseous fluid heated, with may well be incorporated in the Wall of the heatl the products of combustion of the fuel burned to ing furnaee- My invention in the iiI'St described liberate the heat used in the heating operation, form including an open burner iS characterized the burner element is a so-called ribbon burner by the intimate mixture of products of combuswhich extends transversely to the direction of tion with the gaseous fluid heated which is efn iiow of the liquid heated and is encased in refected, and by the fact that when the gaseous no fractory material and discharges products of fluid heated includes combustible constituents, combustion into the heating space. The burner the latter may be readily burned in the heater, is supplied with a combustible mixture of air and with efficient utilization of the heat liberated. fuel gas, and may be, and preferably is, of a type The various features of novelty which charin which the tendency of the ame to blow off acterize my invention are pointed out with paris reduced to a practical minimum, thereby inticularity in the claimsannexed to and forming creasing the safety factor in the use of the ima part of this Speeifloation- For a better Underproved heater. l standing of the invention, however, its advan- My improved air heater is adapted for a wide tages, and Specific objects attained With itS 118e.

,o variety of industrial uses, such, for example, as reference should be had to the accompanying so in heating drawing furnaces, drying chambers, drawingsand descriptive matter in which I have A chambers for annealing non-ferrous metals, stress illustrated and described preferred embodiments relieving furnaces, low temperature glue heating, of the invention. and lithographie, polymerizing and other ovens. Of the drawings:

The form of heater just described has various Fig. 1 is an elevation of a. heater including an 35 advantages, some of which are also obtainable open burner, and of the heater connections, With with a form of my general invention in which a the heater shown in section on the line I--I of heating element in the form of aclosed heater is Fig. 2; located 1n an intermediate portion of a heating Fig. 2 is a plan section on the line 2-'-2 of Fig. l

scribed. In the last mentioned form of the inaway and in section; o

vention, the burner products of combustion are Fig. 3 is a somewhat diagrammatic elevation of notadmixed with air or gas being heated. a heating furnace, orroven, having one form of My improved air heater is characterized in parmy air heating means incorporated in its wall;

5 ticular by its thermal eliciency, its compactness Fig. 4'is a perspective view of a burner assem= 45 and its relatively low inherent cost of manufac.- bly part; ture. The invention is furthercharacterized by Fig. 5 is a section on the line 5-5 of Fig. 6 of the permitted flexibility in its design whereby the an air heater including a closed burner; and size and general form of a unit can readily be Fig. 6'is a section on the line lig-6 of Fig. 5.

made whatever is most convenient for a partic- In the drawings, and referring first to the conm ular use, and` by. the .further fact that the air struction shown in Figs. 1 and 2, A represents the heater may be a mechanical unit of such charrefractory material which surrounds and forms acter and form that a plurality of such units the wall of the heating space, or iowpassage, may be connected in parallel or in series to proof an air or gas heater unit of preferredform.

vide an effective volumetric or temperature rais- As shown, the said space comprises aV burner u chamber C in the form of a horizontal cylinder receiving air or other gas to be heated at its underside through an inlet portion D of the'flow passage, and delivering the gas which is heated, admixed with the heating gases, to an uprising outlet portion E of the flow passage. 'I'he refractory material A is ordinarily enclosed byka metallic housing B.

Mounted in the chamber C, and spaced away from the peripheral wall thereof, is a burner element F encased in and surrounded by refractory material G which is formed at its upper side with a slot G', through which the burning gases leaving the burner, are delivered axially into the passage E. In the preferred form shown, the

burner element comprises a hollow metallic body,

or manifold member, formed with a slot F' in its upper side, and comprises a multiplicity of thin plates H of ceramic material, and comprises means for clamping said plates against the metallic burner body, so that each plate extends transversely across the slot F'. The various plates H are shaped to collectively constitute a wall or body of refractory material of flanged bar form, which closes the slot F', except for burner orifices formed by grooves H' in the side faces of the plates H. As shown, each plate H is provided with shoulder extensions IP for engagement by means clamping it to the burner body, and is formed at its edge remote from the burner body with extensions H3, which form the lopposite sides of a trough-shaped combustion space, to the bottom of which the channels H open. The burner element shown herein comprises various features of construction and arrangement, which are novel with me, but are not claimed herein, as they are disclosed and claimed in my application, Ser. No. 320,189, led Feb. 21, 1940.

The burner body is shown as adapted to receive a. combustible mixture of air and gas at one end, through a supply pipe F2, and in the case of relatively large burners, a combustible mixture supply pipe may be connected to each end of the burner body. As shown in Fig. 2, the burner element has end portions mounted in aligned portions A' of end walls of the chamber C, which are removable to facilitate the insertion, removal, and replacement of theI burner element. As shown, a centering part or shaft-like axial extension, is connected to the end of the burner body remote from the pipe F2. The heat insulation casing or Jacket G for the metallic burner body serves by restricting the transfer of heat between the gaseous iluid being heated and gaseous products of combustion to the burner body, to maintain the metallic burner body at a desirably low temperature.

The type of burner element shown is especially well adapted for its described use, because the ceramic plates H are the only portions of the burner exposed to the heat absorption from the flames, and are well adapted to continuously withstand the temperatures to which they are subjected, and also because a burner of the type shown is adapted for operation with widely different rates of combustion, and in operation with a relatively high rate of combustion, the risk of having its flame blown off is relatively slight. While the type of burner shown is thus especially suitable for use in my improved air heater, those skilled in the art will understand that the air heater may include, and will operate effectively, with burners of other types.

As shown in Figs. 1 and 2, the air or other gaseous iluid to be heated, is moved through the heater by a fan I driven by an electric motor I'. and having its outlet I2 connected to the inlet passage D of the heater. The heatedair or gas is discharged from the heater outlet E, into a. conduit J, shown as jacketed. When the heater is used to heat the gases constituting the atmosphere of a heating chamber or oven, the inlet P of the fan may be connected to an outlet port in the wall of the heating chamber or oven, and the pipe J may lead to an inlet port to the oven chamber.

` To minimize pressure head loss, and to insure an intimate mixture of the air or gas being heat- `ed with the products formed with the combustion of the fuel supplied to the burner element, the flow passage collectively formed by the parts D, C'and E are streamlined. Preferably, the portion of the chamber C at opposite sides of the burner element, are shaped so that each forms a nozzle converging, as does the inlet nozzle of a Venturi passage, while the discharge passage F is shaped to form a. nozzle expanding as does the discharge nozzle of a Venturi passage.

As previously stated, my improved air heating provisions may be incorporated in the wall of an oven or furnace, and one arrangement of the sort is shown in Fig. 3, where K' represents the heating, or oven, chamber of a furnace or oven K, and K2 represents the hearth or bottom wall of the chamber K. A passage L' in the hearth K2 leads from the chamber K to the inlet of a rfan IA, which discharges into oppositely directed discharge passages L'. Each discharge passage L' opens into the bottom wall of a burner chamber CA, formed in the corresponding lower corner of the oven or furnace K. Each chamber CA opens into the corresponding chamber E' through an expanding outlet nozzle passage EA. A burner element FA is disposed in each chamber CA.

Each element FA may be exactly like the burner element F rst described, in general form and in respect to its refractory material casing, and in that it is arranged to discharge burning gases axially into the corresponding discharge passage EA.

For use under conditions making it desirable to avoid admixture of products of combustion with the air or gas being heated, I have devised the form of my invention shown in Figs. 5 and 0. The heater shown in Figs. 5 and 6 comprises a heating space or passage formed in refractory material A, which may be similar in shape to the heating space or passage shown in Fig. l. Actually, however, the single cylindrical burner space C of Figs. 1 and 2 is replaced in Figs. 5 and 6 by upper and lower heater spaces CB and CC. each of cylindrical form. As shown, the two chambers CB and CC have the same diameter, and have their axes separated by a distance somewhat less than the diameter of each chamber, so that the two chambers merge into one another and are connected by a communicating port CD which may be of about the same horizontal width as the upper end of the inlet passage D.

The heater element `shown in Figs. 5 and 6, is of the enclosed burner type. comprising a tubular metallic body having upper and lower horlzontal portions M and MA, each connected at one air in a direction parallel to the axis of the poru rial A at one side of th'e heater, and at the opposite side a pipe P supplies a combustible mixture of air and gas to the burner element 0, and the products of combustion pass from the burner body portion MA into a waste gas discharge pipe p'. Advantageously, and as lshown, the burner body parts M and MA are provided with heat absorbing circumferential ribs or fins Mz of thin metal.v f

'.lhe tubular parts M and MA may be eccentrically located in the chambersCB and CC, respectively. so as to obtain all of the 'streamlining and streamlining advantages obtainablewiththe construction shownin Figs. 1 and 2. With the, type of burner shown inFigs. 5 and 6, lioweven the construction may well be simplied, in some cases, by having the parts M and MA coaxial with the chambers CB and CC, respectively, 'so that the gas passages curving about the opposite sides of the parts MA and MB, between' those parts and the adjacent walls of the chambers CB and CC, respectively, do not change in cross "section along their lengths. p p

While in each of the forms of the invention illustrated, as described, the burner element is shown as horizontally disposed, a burner of either type described, will operate eflicie'ntly 4in any position, so that the burner orifices may be directed upwardly, downwardly, horizontally, or at an angle to the horizontal, as conditions make desirable.

As will be apparent to those skilled in the art, the heater types and forms illustrated and described in detail herein, are Well adapted for their intended purposes and objects. The re1- atively small heater bulk required for a given gasv heating capacity, desirable from the standpoint of space economy, and also because it contributes to low construction cost, is made possible in part, by what I have referred to as the streamlining of the flow passage through the heater. That streamlining makes it possible to keep the maximum cross section of the iow passage small, while keeping the resistance to flow and pressure drop in the heater desirably low. The heaters are designed to secure a relatively high velocity of gas ow over the outer surface of the casing G of the burner elements shown in Figs. l, 2, and 3, and over the parts M and MA shown in Figs. 5 and 6, which contributes to a desirably large rate of heat absorption from the burner element. The relatively high gas velocity in the outlet nozzle portion E, and particularly at the entrance end of the latter, insures that under all practical operating conditions, the flow is sufciently turbulent to insure rapid equalization of the temperatures of all portions of the uid flowing through the outlet passage, and such relatively high gas velocity also insures uniform admixture of the products of combustion with the gas being heated.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the forms of apparatus disclosed, without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may be used to advanelongated heating element .located in and extage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: l

1. A heater for gaseous material, comprising refractory material surrounding and forming a heat insulating wall for a streamlined iiow passage including one or more chambers, each extending transversely to the length of said passage, and inlet and outlet portions opening to said chamber or chambers at opposite sides of the latter and each increasing in cross section as the distance -from'said chamber increases, and an tending longitudinally of each such chamber and spaced from the waliof said chamber to provide passages at'the opposite. sides of the elementthrough which the gas passing from said inlet portion to said outlet portipn, flows in divided streams. Y

2. A heater for gaseous material, comprising a flow passage including a heating chamber extending transversely to the length of said passage, and inlet and outlet portions opening to said 25 burner chamber at opposite sides of the latter, an elongated burner located in and extending longitudinally of said chamber and spaced from the wall of said chamber to provide passages at the opposite sides of the burner element through lwhich the gas to be heated ows in divided streams from said inlet portion to said outlet portion, said burner having an inlet for gaseous fuel and having burner orifices opening to said passage.

3. A heater for gaseous material, comprising refractory material surrounding and forming a heating insulating wall for a flow passage, said passage including a burner chamber extending transversely to the length'of said passage, and inlet and outlet portionsopening to said burner chamber at opposite sides of the latter, a burner located in and extending longitudinally of said chamber and spaced from the wall of said chamber to provide passages at the opposite sides of the burner element through which the gas to be heated flows in divided streams from said inlet portion to said outlet portion, said burner being formed with a fuel space and with burner orices opening from said space toward the outlet portion of said passage.

4. A heater for gaseous material, comprising a iiow passage surrounded by a-heat insulating wall of refractory material and including an elongated cylindrical burner chamber extending transversely to the length of said passage, and inlet and outlet portions opening to said burner chamber at opposite sides of -the latter, a burner located in, and extending longitudinally of said chamber andcomprising a hollow metallic body portion and an outer portion of refractory material, 'spaced from the wall of said chamber to provide 'passages at the opposite sides of the burner element through which the gas to be heated flows in divided streams from said inlet portion to said outlet portion, said burner having a fuel space within said hollow body and burner orifices opening to said passage.

5. A heater for gaseous material, comprising a flow passage including an elongated burner chamber extending transversely to the length of 'n said passage, and inlet and outlet portions opening to said burner chamber at opposite sides of the latter, a ribbon burner adapted for the combustion of a combustible mixture of air and gas, located in and extending longitudinally of said u chamber and spaced from the wall oi said chamber to provide passages at the opposite sides of the burner element through which the gas to be heated ows in divided streams from said inlet portion to said outlet portion, said burner having a combustible mixture chamber and burner orirlces opening from said chamber toward the outlet portion of said passage.

6. A heater for gaseous material, comprising refractory material surrounding and forming the wall of a streamlined ow passage including an outlet portion of expanding nozzle form and an inlet portion in line with said outlet portion, a burner element in said passage between the inlet and outlet portions thereof and comprising an outer portion of refractory material in positionto be engaged by uid owing through said passage, and formed with a fuel space and with burner oriilces opening to said passage adjacent the inlet end of said outlet portion.

'7. A heater for gaseous material, comprising a flow passage including a burner chamber extending transversely to the length of said passage, and inlet and outlet portions opening to said burner chamber at opposite sides of the latter, an elon'- gated burner located in and extending longitudinally of said chamber and spaced from the wall of said chamber to provide passages at the opposite sides of the burner element through which the gas to be heated flows in divided streams from said inlet portion lto said outlet portion, said burner having an inlet for gaseous fuel and having burner orifices opening to said passage and separate means for passing gaseous material to be heated into said flow passage and for passing a combustible mixture into said fuel space.

8. .A heater as specified in claim 7, in which the said ow passage is surrounded by a heat insulating wall of refractory material.

FREDERIC O. HESS.

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