US2564258A - Multiple annular heat transfer element forced flow air heater - Google Patents

Description

Aug. 14, 1951 G. B. HERBSTER 2,564,258

MULTIPLE ANNULAR HEAT TRANSFER ELEMENT FORCED FLOW AIR HEATER Filed April 21, 1950 8 sheeis-sheet 1 INVENTOR. GEORGE B. HERBSTER.

A TTORNEY.

G. MULTIPLE ANNULAR HEAT TRANSFER ELEMENT 2 FORCED FLOW AIR HEATER B. HERBSTER Aug. 14, 1951 Filed April 21, 1950 8 Sheets-Sheet 2 "I IN V EN TOR.

GEORGE B.HERB5TER.

ATTORN EY.

' Filed April 21, 1950 Aug. 14, 1 9.51

- G. B. HERBSTER 2,564,258 MULTIPLE ANNULAR HEAT TRANSFER ELEMENT FORCED FLOW AIR HEATER 8 Sheets-Sheet 3 Y INVENTOR.

GEORGE B. HERBSTER.

1 BY E MULTIPLE ANN ULAR HEAT TRANSFER ELEMENT 1951 G B. HERBSTER 2,564,258-

FORCED FLOW AIR HEATER Aug. 14, 1951 v G. B. HERBSTER 2,564,258

MULTIPLE ANNULAR HEAT TRANSFER ELEMENT FORCED FLOW AIR HEATER Filed April 21, 1950 8 Sheets-Shet 5 R 3 s ff 0 Q! l & L\ m a c f a E i i l no I M I w l j i Z I Z I 4 \i 5 a: 00 Ki N W R 1 g1 INVENTOR.

g QEORQL B. HERBS ER.

Aug. 14, 1951 G. B. HERBSTER 2,564,258 MULTIPLE ANNULAR HEAT TRANSFER ELEMENT FORCED FLOW AIR HEATER Filed April 21., 1959 8 Sheets-Sheet 6 INVENTOR; GEORGE B.HERBSTE.R.

" A T TORNEY.

- G. B. HERBSTER 2,564,258 MULTIPLE ANNULAR HEAT TRANSFER ELEMENT FORCED 110w AIR HEATER Filed April 21, 1950 v s Sheets-Sheet 7 Aug. 14, 1951 INVENTOR. GEORGE B. HERBST ER.

ATTORNEY.

Aug. 14, 1951 G. B. HERBSTER 2,564,258

MULTIPLE ANNULAR' HEAT TRANSFER ELEMENT FORCED FLOW A IR HEATER Filed April 21, 1950 -8 Sheets-Sheet 8 Zmventor GEORGE BEHERESTEVRY Patented Aug. 14, 1951 MULTIPLE ANNULAR HEAT TRANSFER ELE- MENT FORCED FLOW AIR HEATER George B. Herbster, Cleveland, Ohio, assignor, by mesne assignments, to 8600 Denison Company, Cleveland, Ohio, a corporation of Ohio Application April 21, 1950, Serial N 0. 157,222

11 Claims. 1

This invention relates to heaters, and particularly to a compact and efficient forced circulation heater arranged to recirculate air directly in the room or space in which the heater is located or from a central location through other rooms or spaces, and is a continuation-in-part of my copending application Serial No. 663,506, filed April 19, 1946, which application has become abandoned.

One of the principal objects of the present invention is to provide a heater in which air to be heated is passed into more efficient heat exchange relationship with a heat exchanger and is circulated through the heat exchanger and in or to the space to be heated in a different and more efiicient manner.

A more specific object of the present invention is to provide a heater in which the air to be heated is admitted centrally of the heater and caused to flow radially of the heat exchanger thereof and to discharge generally radially from the heat exchanger into the space in which the heater is located or into a suitable plenum chamber from which it is conducted to points of application through suitable ducts. Another object is to increase the heat exchange relation between the surface of the heat exchange means and the air by providing a Venturi effect in the air passages which causes more efficient contact of the air and surface and breaks up and reduces the usual insulating air skin effect on the surfaces without materially increasing the resistance to flow of the air through the heat exchange means.

Another object is to provide a heater in which the heat exchanger or heat exchange means can be assembled from a plurality of identical heat exchange heads, each of which is formed of a pair of identical sheet metal sections and in which exchanger, when the heads are assembled, a large heat exchange surface and adequate passage of air are provided and so related that efiicient heat exchange relationship between the surface and air results.

Another object of the invention is to provide a heater oi the character described which is compact and durable and may be manufactured economically.

Other objects and advantages will become apparent from the following. description, wherein reference is made to the drawings, in which:

Fig. 1 is a front elevation of a heater embodying the principles of the present invention;

Fig. 2 is a side elevation of the heater illustrated in Fig. 1;

Fig. 3 is a vertical sectional view at right angles to the horizontal axis of the heater illustrated in Figs. 1 and 2 and is taken on the line 3-3 of Figs. 2 and 4, part thereof being shown in elevation for g clearness in illustration;

, Fig. 4 is a vertical sectional view of the heater and is taken on line 4-4 of Figs. 1 and 3;

Fig. 5 is a horizontal sectional view of the heater taken on the line 55 of Figs. 1 and 3;

Fig. 6 is a front elevation of a modified form of the heater, part thereof being shown in section as indicated by the line 6-6 in Fig. 7;

Fig. is a vertical sectional view of the heater illustrated in Fig. 6 and is taken on line 1--1 thereof;

Fig. 8 is a vertical sectional view of another modified form of the heater and is taken on the line 8-8 of Fig. 9;

Fig. 9 is a vertical sectional view of the heater illustrated in Fig. 8 and is taken on line 9-9 thereof;

Fig. 10 is a sectional view of the heater illustrated in Figs. 8 and 9 and is taken on line l0l0 of Fig. 9;

Fig. 11 is a front elevation of a heat exchange head which may be used in the heater as illustrated in Figs. 1 through 10;

Figs. 12 and 13 are front elevations, respectively, of heat exchange heads which may be used in the heater illustrated in Figs. 1 through 10;

Fig. 14 is a fragmentary sectional view of the heat-exchange head'of Fig. 12 and is taken on line MM thereof;

Fig. 15 is a front elevation of a modification of a heating head, part thereof being broken away for clearness in illustration;

Fig. 16 is a fragmentary sectional view taken on line l6-l6 of Fig. 15.

Fig. 17 is a front elevation of another modification of a heating head; and

Fig. 18 is a fragmentary sectional view taken on line I8l8 of Fig. 17.

Referring to Figs. 1 through 5, the present invention is shown as embodied in an oscillating suspended type of space heater of the general character described in my U. S. Letters Patent No. 2,336,669, issued December 14, 1943, its embodiment in other types of heaters being readily apparent from the illustrative example.

As illustrated in Figs. 1 through 5, the heater comprises generally an outer casing comprising a front wall or cover I and a rear wall or cover 2 which are joined by a peripheral wall 3. The front wall or cover I is preferably a generally Circular annulus of Sheet metal having its inner and outer peripheral margins curved away from its normal plane so as to form a relatively shallow annular dish-like structure having a central opening or passage 4. The central passage 4 of the front wall or cover I is spanned by a suitable spider which is connected at its ends to the inner periphery of the cover and supports a plurality of annular frusto-conical vanes 6 which are accommodated in the opening 4 and are spaced apart from each other radially of the cover I to provide air passages I therebetween which are shaped so that air entering therethrough is directed in annular paths convergent inwardly of th casing and toward the axis of the passage 4.

The wall or cover 2 is identical with the cover I, having a central opening or passage spanned by a spider 8 to which are secured annular vanes 9, the series of the vanes 6 and 9 preferably being identical and aligned with each other axially of the covers I and '2. The peripheral wall 3 is preferably in the form of a band of sheet metal formed into a cylinder and having its margins inturned and fitted between the outer peripheral margins of the covers I and 2, as best illustrated in Fig. 5, the covers I and 2 being spaced at opposite ends of the wall 3 in axial alignment in a position in which they are concave toward each other. The peripheral wall 3 is provided with a plurality of air outlet passages I0, each of which may be provided with a vane II for directing the air issuing therefrom generally downwardly.

Mounted within the casing are bafile walls I2 and I3 having central passages l4 and I5, respectively, which are coaxial with the central passages of the covers I and 2. The walls I2 and I3 have outturned margins which engage the inner surface of the outer margins of the covers I and 2 and also the lateral margins of the wall 3 so as to provide a central heating compartment which is uncommunicated with the remainder of the casing except through the central passages l4 and I5.

Mounted between the walls I2 and I3 is the heat exchanger or heat exchange means of the heater. For the purposes of illustration, the heat exchange means are shown as heated by com bu'stible media, such as gas, though other heatin media may be employed if desired. In the illlustrative example, the heat exchange means comprises a plurality of generally annular hollow heat exchange heads I 6 which are arranged in a row in axial alignment with each other and with the central passages I4 and I5 of the walls I2 and I3. The heat exchange heads are arranged in face to face spaced relation to each other so as to provide generally radially extending passages for air, as indicated at I l, therebetween. The heat exchange heads, in the form illustrated, are shown as generally disc-like in structure though they may be frusto-conical annul'i if desired. Each head I6 has a central passage I8 and the passages I8 are aligned with each other axially and with the central passages I4 and I5, thus defining therewith a central passage for the heat exchange means as a whole.

It is apparent from the foregoing description that air may be circulated through the passages 1 between the vanes 6 and correspondingly through the passages between the vanes 9 and thence through the passages I4 and I5 into the central passage defined by the central openings I8 of the heat exchange heads. From the latter the air may circulate generally radially of the heat exchanger through the passages I! between the adjacent heat exchange heads I 6 and between the baffle walls I2 and I3 and the heads adjacent thereto, respectively. This fiow of air may be in either direction but it is preferred, in order to obtain a better distribution of heated air in the room, to introduce the air into the central passages I8 and discharge it from the heater generally radially through the radial passages I! between the heads and the passages It in the cas- For this purpose, a blower I9 having a rotor 20 may be provided. The rotor 20 is preferably of the squirrel cage type having a central shaft 2| with spokes 2'2 radiating therefrom and carrying fellies 23 on which are mounted the air impelling blades 24.

In order to support the rotor 20 within and in coaxial relation to the central passage through the heat exchange means, the blower shaft 2I may be an integral part of the drive shaft of a suitable motor 25. The motor 25 is mounted in a bracket 26 supported by a suitable spider 21 which is carried by the baffle wall I2. A suitable cap 28 may be snapped onto the outer end of the motor, if desired, the cap 28 having its peripheral walls conforming generally in shape to the vanes 6. The opposite end of the shaft 2| is mounted in the housing er a suitable reduction gear transmission, indicated generally at 30, which is carried by a bracket 3I supported by a spider 32 which is carried by the baffle wall F3.

The rotor 23 is preferably of such length axially that it terminates at or slightly inwardly from the bafile walls 52 and i3, and the inner peripheral margins of the walls I 2 and I3, defining the passages Hi and I5 may be curved inwardly of the casing, as illustrated in Figs. 4 and 5, so as to constrain the air entering the passages I and I5 to pass to the inside of the rotor 29 and to pre= vent air, due to back pressure between the walls i2 and 53, from passing back out through the openings I4 and I5. Thus when the blower is operated, air is drawn in between the vanes of the covers I and 2 and passes through the central passages It and I5 of the walls 12 and I3 and enters the inside of the rotor 20 and is discharged radially outwardly therefrom through the passages il between the heat exchange heads I6 and between the walls ['2 I3 and the heat exchange heads adjacent thereto, resp%tively-, and then is discharged at the peripheries of the heat exchange heads l8 and passes outwardly through the openings Ill in the peripheral wall 3 where it may be directed by the van-es I I "downwardly or in such direction as may be desired, depending upon the shape and "direction of the vanes I I.

In order to oscillate or rotate the heater about a vertical axis a suitable hanger 355 is provided and may be secured to an overhead support by means of bolts 35. The hanger'35 has a stationary external bevel gear 3'! which isexposed down,- wardly and is engaged by a complementary bevel gear 38 which is mounted in the heater casing for rotation about a fixed axis, as illustrated in Fig. 4. The gear 38 is driven rotatably by a shaft 39 which, in turn, is driven through the medium of the reduction gear transmission 36 and shaft 2l of the motor 25. Thus when the blower is being operated it drives the gear 38 through the medium of reduction gearing Eli and since the hanger is fixed in position, it causes the gear 38 to planetate about the gear 3?, thus rotating the heater about the axis of the gear 3i.

For supporting the heater rotatably in posi-t'ien 5. with respect to the hanger 35, a suitable: annular bearing 40 is fixed in position with respect to the heater and rests on suitable ball bearings M which are interposed between its undersurface and the upper bearing surface of the hanger 35.

-In order to adapt the heater for use with com-. bustible gaseous heating media, each of the heads I6 is provided with a combustion .portion 45 and an exhaust stack portion 46.- As best illustrated in Figs. 3 and 4, all of the combustion portions 45. are seated individually in sealed relation; in the top of a suitable common casting 4'! which ex-'-. tends downwardly from the portions 45 andis hollow and open at the bottom to accommodate a burner 48 and to admit secondary air for sustaining combustion at the bottom. The burner 48 is provided with a plurality of head portions 49, each of which projects upwardly slightly into the compartment 45, of an associated one of the heads I6. Gas is supplied to the burner 48 through a suitable stationary injection nozzle 50, primary air being induced through the mixing bell 5| of the burner.

As more fully described in my above identified patent, the nozzle 58 and the mixing bell 5| are exactly on the vertical axis of rotation of the heater so as to be in coaxial relation with each other at all times during rotation of the heater. The heating media and products of combustion, therefore, are introduced into theinterior of the hollow heads I6 and fiow upwardly therethrough without coming into contact with any air being circulated for heating.

The stack portion 46 of each of the heads I6 is diametrically opposite from its combustion portions 45. The stack portions 46 are individually in sealed telescopic relation with a single exhaust header 53, to which the annular bearing 40 may be fixedly secured for rotatably suspending the heater. The products of combustion from all of the heads I6 are thus exhausted through a common stack portion 5 3 of the header 53 which likewise is coaxial with the vertical axis of rotation of the heater so that it can be in telescopic relation with the exhaust stack from th room for venting the products of combustion during rotation of the heater. The header 53 is fixedly secured to the bafiie walls I2 and I3 for supporting the heater in suspended condition by the header.

Referring next to the specific structure of the heat exchange heads 56, each of the heads is pref erably formed of two identical annular discs of sheet metal which are corrugated and placed in symmetric relation to each other and secured together at their inner and outer peripheries. The corrugations of each section of each head are preferably annular and extend from the combustion portion 45 to the stack portion 46 thereof. The corrugations of one section are aligned axially of the sections with the corrugations of the other section so that when the sections are joined together in symmetrical relation and axial alignment, the corrugations define a plurality.- of passages I50 which are arcuate about the axis of the heads and communicate with the combustion chamber portion 45 with the stack portion 46 of the joined sections. Thus the heating media may pass from the combustion chamber portion 45 of each head through the head-in arcuate paths to the exhaust portion 46. For this purpose, the corrugations are preferably arranged so that the inner adjacent crests of the correspondingcorrugations of each of the sections arein juxta- 6 position with each other as indicated at 6 I. Fur thermore, the corrugations are preferably of such shape that when two heads are placed in spaced relation to each other, the corrugations of their adjacent faces define the passages I! which are arcuate and generally radially extending. Each of the passages I1 is first abruptly contracted in adirection from the inner periphery toward the outer periphery of the heads, as best illustrated in Fig. 5 and then less abruptly expanded, this contraction and expansion continuing in sequence to the outer periphery so that each passage i1 is in the form of a plurality of arcuate Venturi tubes discharging successively from one into the other. As a result of this structure a larger. heat exchange surface is exposed to the traveling air as well as to the heating media and at the same time the air passing radially through the passages is maintained in better heat exchange contact with the heat exchange heads without any serious resistance to flow and the dead air skin effect on the surfaces of the heads is broken up or reduced. The capacity of the blower 20 preferably is such as to maintain a positive pressure between the heat exchange heads and in the compartment defined by the bafile walls I2 and I3 so that the air delivered by the blower is constrained to pass through the central passages of the heads and flow radially outwardly between adjacent heads and between the walls I2 and I3 and the heads adjacent thereto to the points of discharge.

To hold the casing parts and baflie walls in proper relation, suitable spacing posts 64 may be provided and extend through the baffle walls I2 and I3 and therebeyond so as to abut the front and rear covers I and '2 of the heater cabinet. Suitable bolts '65 extend through the covers I and 2 and are received in threaded engagement with the spacing posts 64 for securing the covers I and 2 firmly in place with respect to each other and to the circumferential wall 3. The baffle walls I2 and I3 may be welded to alternate ones of the posts 64, respectively, if desired. Such a struc-v ture may be readily assembled by assembling the heads I6 in the castings 41 and 53, placing baflle walls l2 and I3 in place and by means of the bolts 65 and posts 64 firmly clamping this assemblage between the covers I and 2. For servicing of the motor and blower, the covers I and 2 may readily be removed Wthout disturbing the remainder of the assemblage.

Referring next to Figs. 6 and 7, a modified form of the heater is illustrated in which the individual heating heads Iii, similar in form and function to the heads I6 heretofore described, are provided to form the heat exchange means and are accommodated between a front bafile wall II and a rear baflie wall I2. The front bafile II is provided with a central opening or passage I3 within which is a propeller fan 14. A motor 15 for driving the. fan I4 is supported in a suitable bracket 16 carriedby the spider II which may be formed integral with the baiile wall I I. In this form .of the invention, the cabinet is provided with a forward wall I8 having central opening I9 with vanes therein which are similar inform and arrangement to the vanes '6. Heat is supplied into the hollow heads ID by a burner BI in the manner heretofore described so that the products of combustion and heating media fiow through the heat exchange heads and are exhausted through a suitable stack 82. The fan I4 has sufiicient delivery to maintain a positive pressure between thewalls II and I2 so that the air is drawn in between the vanes Bi] and is forced through the central passage of the heat exchange means, which passage is defined by the central openings of the individual heads 70., and flows radially outwardly-between the heads about the circumferential portions thereof extending between the combustion chamber portion =83 and exhaust portion 3-4 of each head. In this form of the invention, the cabinet is provided with a plurality of openings '35 in its peripheral walls and suitable directional vanes 86 are formed by bending outwardly the metal severed for forming the openings 85. In this type of heater also the air is drawn in at the forward end and delivered to the heat exchangers centrally thereof and discharged generally radially from the heat exchange heads and from the heater cabinet through the openings 65.

In Figs. 8, 9 and 10, there is illustrated another form of the heater embodying the principles above described but which is adapted for a centralized or basement type heating unit. In this form of the invention the heating heads 90, similar to the heads I5 and W, are correspondingly arranged and heating media are supplied thereinto by a burner 9i and exhausted therefrom through a suitable stack 92 common to all of the heads. Air is supplied to the aligned central passages of the heads through a suitable duct '93 by means of a blower 9d driven by a suitable motor 95. Baflle walls 95 and 91 are provided for constraining the air delivered through the duct 93 to pass radially between the heads and between the walls 36 and 91 and th heads adjacent thereto and to prevent the air delivered into the central passage of the head from entering the combustion chamber and the staclr. The walls es and s1 terminate upwardly in a plenum chamber 98 from which the heated air is distributed through suitable ducts to points of application. All of this structure is enclosed in a suitable cabinet 99 which has a return inlet passage me for admitting air into th interior of the cabinet 99 from which it can enter the open ends of the blower 94. The particular advantages of the casing 98 in this central type of heater is that it provides a large area for filter space without restricting the admission oiair to the blower. Within the casing 99 are a plurality of replaceable filters IE3! which may be so arranged as to necessitate that all of the air passing to the blower 9'3 pass through the filters.

Referring next to Figs. 11 through 14, the structure of the heads for adapting them for different sizes and cabinets without unduly increasing the number of dies required are illustrated. Asheretofore mentioned, the heat exchange heads described herein are preferably circular. If for any reason a different size head is desired without any greater width, a head I 3 such as illustrated in Fig. 11 may be employed. As there illustrated, the head Hi4 theoretically may be assumed to be in three sections, divided along the dot-dash lines I05 and I06. The upper portion I01 is the upper half of a circular head, such as the head It heretofore described, and the lower portion I08 is the lower half of such a circular head. A central portion his is provided with straight corrugations Il0 which, at their upper and lower ends, are tangent to the annular corrugations of the semi-circular head portions I01 and 108. Accordingly, a large number of heads can be made with a single set of dies made for the heads I6 merely by splitting the dies and inser'ting a simple corrugated die insert comparable to the head portion I09 between the more expensive semi-circular die portions comparable to the head portions I01 and I08. Obviously, if no die insert is interposed to provide the portion 109, a circular head I6 can be formed and any number of annular heads of the same Width but of greater height can be provided by the choice of proper sizes of inserts for the portion I09.

Again, and for the same reasons, it may be desirable to form the heads of greater width but of fixed height in which case the head sections may be formed as illustrated in Figs. 12 and 13. Refer-ring first to Fig. 12 there is shown a head section III which is annular but somewhat elliptical, thus giving a greater width with a fixed height. Such a head section is made by means of a die divided into an upper section and a lower section along the line I I2. When such die sections are together, a head section I I I is formed but such die sections can be moved apart in a direction normal to the dividing line II2 for the interposition of inserts, of the general type described in connection with Fig. 11.

In Fig. 13 a head section so formed is illustrated. In this form, the upper and lower die sections used for forming the head section of Fig. 12 are moved apart, as indicated by the lines H3 and H4, so that the upper half H5 of the head section and the lower half I I6 are the same as the upper and lower head sections of the head HI. The central section II='I is formed by interposing an insert of the height desired and corrugated so that the corrugations thereof are tangent at their ends to the corrugations of the upper section I I5 and the lower section I I3. Thus for a given width, a wide variation in height is permitted.

It is apparent from the foregoing description of the manner in which the head sections are formed, that a Wide range of head sections of various Widths, heights, and total capacities may be provided merely by a number of the straight corrugated inserts and without any larg number of the expensive and basic arcuate or curvilinear portions of the dies.

As heretofore explained, the head sections of all of the heads are made of two sheet metal stampings, joined together at their inner and outer peripheries, and tacked together, if desired, by welding or otherwise at the juxtaposed wall portions between the corrugations. The sections for a given head are congruent and both are formed from the same die. They are then placed together in coaxial alignment with their corrugations symmetrically arranged but on opposite sides of the line of juncture.

As illustrated in Fig. 14, one head section I20 of the heating head III is placed with the troughs I22 'of its corrugations in juxtaposition with the corresponding troughs I23 of the corrugations of a congruent head section I2I. The head section I2I is formed of a slightly smaller sheet than the head section I20 so that the inner and outer peripheral margins I24 and I25 of the section I20 can be folded over the peripheral margins of the section I2I. Soft metal wires I26 and I 21, such as copper are interposed respectively between each of the folded over portions I24 and I25 and the corresponding peripheral margins of the section .I2I so that when the portions I24 and I25 are rolled or stamped firmly into position, the wires are compressed and deformed into a gasket =or seal to prevent leakage at the inner and outer peripheries of the heads.

As mentioned, the troughsof the corrugations of the sections may be spot welded together if desired to provide greater rigidity and strength but leakage therebetween from one of the annular hollow or tube portions of a head to another such portion of the head is inconsequential.

It is apparent from the foregoing description that a heater can be provided readily at a minimum expense inasmuch as the front and rear covers I and 2 of the cabinet ma be congruent and made from a single set of dies and each section of each of the heads may be made from a single set of dies. formed by stamping and each may be formed in a Single operation. Likewise the vanes 6 and S'may be made from the same series of dies, and the peripheral wall of the cabinet with passages Ill and vanes I I may be made from a single band of sheet metal in a simple stampin operation.

Referring next to Figs. 15 through 18, other modifications of one of the heads are shown, these modifications being directed to other means for effecting distribution of the combustion media radially of the heads and preventing the localization or concentration of the major portion of the media passing upwardly through the heads near the inner periphery. The heads in other respects are similar to the heads heretofore described and correspondingly arranged in the heater.

In Figs. 15 and 16 a head I29 is illustrated. In this form each hollow portion may be of gen erally uniform width endwise of the row of heads from near to its inner periphery to near to its outer periphery. In order to obtain a plurality of generally upwardly directed spaced paths of flow for the media, a plurality of bafiles I30 are provided in the heads. These may be in the form of small angles of sheet metal having one flange, as indicated at I3I, welded to theinterior wall of the head and the other flange extending crosswise of the passage and generally across the path of flow of the media. These may be placed on opposite walls if desired and preferably are installed by welding prior to assembling the two sections to form the head. They operate to cause the media to flow in spaced paths, as indicated by the arrows in Figs. 15 and 16. In order to prevent cold spots to the rear of each bafiie in the direction of flow of the media, that flange of each baflle which extends across the passage through the hollow portion preferably is provided with perforations, such as indicated at I32 in Fig. 16.

In Figs. 17 and 18 a head I33 is shown in which baflles I34 are provided, the baffles I34 being in the form of elongated sheet metal elements of L-shape cross-section. Each is arranged with one flange welded to the interior surface of the head. The flanges of the angles I 34 which extend across the passage are preferably curvilinear and concentric with the central opening and extend lengthwise about the axis of the central opening and thus generally along the path of flow of the media, thus dividing the stream of media into a plurality of paths and constraining the major portion of the media from localizing near the inner periphery.

Having thus described my invention, I claim:

1. In a heater, a plurality of upright generally annular hollow heads arranged in a row in axial and spaced face to face relation to each other and providing a central passage with gen erally annular radial passages between adjacent heads communicating with the central passage, each head being narrow in width endwise of the row relative to the radial dimension from its inner to its outer periphery and comprisin an All of these parts may be' 10 inlet portion extending from near to its inner periphery downwardly and opening downwardly and an exhaust portion extending from near to its inner periphery upwardly and opening upwardly, said inlet and exhaust portions of each head being relatively narrow endwise of the row of heads and elongated in horizontal section in the plane of the head, and each head further comprising two groups of generally arcuate concentric generally tubular portions, extending about the central passage, one group clockwise and one counterclockwise, from the inlet portion to the exhaust portion, each of the generally tubular portions of said groups being in communication at its lower end with the inlet portion and at its upper end with the exhaust portion, power driven blower means arranged at the central passage to cause air to enter the central passage and to force said air therefrom out through the radial passages, fluid fuel burner means respective to the heads and arranged to discharge separately directly upwardly in the inlet portions in spaced relation to the walls thereof to sustain combustion in said inlet portions, respectively, the inlet portion of each head being spaced, endwise of the row of heads, from the inlet portions of adjacent heads from the upper end of the inlet portions downwardly at least near to the upper level of the burner means, and the exhaust portion of each head being spaced, endwise of the row of heads, from the exhaust portions of adjacent heads, from the lower ends of the exhaust portions upwardly at least near to the level of the upper limits of the outer generally tubular portions, whereby each of said radial passages is continuous circumferentially of the heads, and the adjacent walls of adjacent inlet portions andadjacent walls of adjacent outlet portions are swept by said air.

2. A heater according to claim 1 characterized in that each generally tubular portion of each group is in contact at its peripheries with those generally tubular portions of the same group which are radially adjacent thereto.

3. A heater according to claim 1 characterized in that the corresponding generally tubular portions of the row of heads are generally aligned endwise of the row of heads with each other so as to render the radial passages repeatedly convergent and divergent from their inner to their outer peripheries.

4. A heater according to claim 1 further characterized in that the walls of said heads are of and an exhaust portion extending from near to its inner periphery upwardly and opening upwardly, said inlet and exhaust portions of each head being relatively narrow endwise of the row of heads and elongated in horizontal section in the plane of their head, and hollow portion extending about the central passage, one clockwise and one counterclockwise, from the inlet portion to the exhaust portion, each of the hollow portions being in communication at its lower end with the inlet portion and at its upper end with the exhaust portion, power driven blower means arranged at the central passage to cause air to enter the central passage and to force said air therefrom out through the radial passages, a fluid fuel burner means having portions respective to the heads and arranged to discharge combustible media separately directly upwardly in the inlet portions in spaced relation to the walls thereof to sustain combustion in the inlet portions, respectively, the inlet portion of each head being spaced, endwise of the row of heads, from the inlet portions of adjacent heads from the upper ends of the inlet portions downwardly at least near to the upper level of the burner means, and the exhaust portion of each head being spaced, endwise of the. row of heads, from the exhaust portions of adjacent heads from the lower ends of the exhaust portions upwardly at least near to. the level of the upper limits of the said hollow portions, whereby each of said radial passages is continuous circumferenti'ally of the heads and the adjacent walls of adjacent inlet portions and adjacent walls of adjacent exhaust portions are swept by said air, and each hollow portion including means providing a plurality of generally upwardly directed spaced paths of flow for the media.

6. A heater according. to claim. 5 characterized in that each head comprises two: substantially duplicate generally annular disc-like sheet metal sections, each section having portions offset from the general plane of the section which prov-ides substantially half of the inlet portion andhalf of the exhaust portion, respectively, and having radially spaced cireumferentially extending corrugations forming substantially half of the generally tubular portions, respectively, and said sections being arranged. incoaxial relation to each other and facing opposite directions and secured together at their inner and outer peripheries, respectively.

'7. A heater according to claim 5 characterized in that the burner means comprises a burner having separate head portions respective to the hollow heads and arranged to discharge separately directly upwardly into the associated inlet portions of the heads; respectively; in spaced relation to the Walls thereof.

8. A heater according to claim 5 characterized in that a closed top burner compartment is arranged beneath the heads and encloses the: burner, and has openings in its top wall respective to and communicating with the lower ends: of the inlet portions, said burner being: closely adjacent the bottom of the inlet portions and having portions respective to the heads and arranged. to. discharge directly upwardly in spaced relation to. the walls of the inlet portions.

9. A. heater according to. claim 5 characterized in that said blower means includes. a rotary blower radial discharge. impeller which is: open for receiving an axially at: at least one end, and means rotatably supporting said impeller in and coaxial with. said central passage,

10-. A heater according to claim 5. characterized in that at least the outer faces of the hollow portions of each head are inthe shape of corrugations which extend circumferentially' of the head about the axis of the central opening.v

11-. A. heateraccording' to claim 5' characterized in that the means. providing a plurality of generally' upwardly directed spaced paths of flow for the media in each hollow portion are. bafll'es arranged within the hollow portions, respectively.

GEORGE B. HERBSTER.

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

UNITED STATES PATENTS France Jan. 3, 19-22

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