US3451388A - Wall furnace - Google Patents

Description

June 24, 1969 J. D. ECK 3,451,388

WALL FURNACE Fil ed Jan. 15, 1968 Sheet 0f 2 FIG. I

INVENTOR.

JOEL D. ECK

Maw

ATTORNEY Julie 24, 1969 .1. D. ECK 3,451,388

WALL FURNACE Filed Jan. 15, 1968 Sheet 2 0f2 FIG. 4

I NV E NTOR.

JOEL D. ECK

ATTORNEY United States Patent 3,451,388 WALL FURNACE Joel D. Eck, Lincoln Township, Sedgwick County, Kans.

- (Rte. 2, Valley Center, Kans. 67147) Filed Jan. 15, 1968, Ser. No. 697,862 Int. Cl. F24h 3/00; F281 13/08; F23m 9/00 U.S. Cl. 126116 10 Claims ABSTRACT OF THE DISCLOSURE A wall furnace including spaced front and rear heat exchanger units respectively upwardly and downwardly tapered to define an upwardly and forwardly inclined convection zone therebetween. The front heat exchanger is provided with a removable baffle structure therein for alternately deflecting rising combustion products from a burner at its lower end forwardly and rearwardly. All except the lower end portion of the interior of the rear heat exchanger is laterally separated into two portions, and the upper ends of such two portions are connected respectively to the upper interior of the front heat exchanger and to a chimney connector. The lowermost end of the rear heat exchanger is open and bafile means is provided in the two interior portions of the rear heat exchanger for the purpose of stabilizing or equalizing pressures to obtain a more uniform draft despite the chimney being exposed to wind gusts and also for the purpose of enhancing heat exchange contact of the walls of the rear heat exchanger with combustion products passing therethrough. A shield is disposed between the front and rear heat exchangers to reduce radiant heat exchange therebetween and to separate the convection zone into front and rear zones, and a deflection plate is mounted on the top of the rear heat exchanger to facilitate direction of convection currents rising from the zones and from the rear of the rear heat exchanger toward the top vented upper end of the front wall of the furnace.

The present invention relates to new and useful improvements in Wall furnaces, and more particularly relates to improved heat exchanger means for effecting transfer of heat from hot combustion products to air circulating through the furnace while minimizing the front to rear dimensions of the furnace, and wherein such heat exchanger means is so constructed as to achieve an equalizing or balancing action such that the draft to which the burner is subjected is maintained relatively constant despite the chimney being exposed to wind gusts.

Wall furnaces have long been known as exemplified by U.S. Patent No. 2,792,826 entitled Forced Air Wall Heater which issued May 21, 1957 to Kilbury, and U.S. Patent No. 2,482,369 entitled Air Heating Wall Furnace, which issued Sept. 20, 1949 to Rhodehamel, and the present invention is generally directed to accomplish the same objectives and to realize performance of the same functions as the apparatus disclosed in such patents, such disclosures being incorporated herein by reference.

Supplementing the objectives of prior art wall furnaces such as exemplified by the above mentioned U.SL patents is the paramount object of the instant invention to effect an increase in the efiiciency of the transfer of heat from heated combustion products to air circulating through the furnace for any given overall volume of space occupied by the wall furnace and/or to realize on reduction of the overall volume of the wall furnace (particularly that resulting from reducing the front to rear dimension) as great an efiiciency of heat transfer as heretofore attained by prior art proposals which do not employ forced air circulation.

Still another important object of the instant invention Patented June 24, 1969 eration and in which replacement of parts most subject to the most deleterious effects of high temperature and chemical attack are readily removable and replaceable.

A broad aspect of the invention involves a wall furnace of the type including an upstanding generally rectangular housing adapted for positioning in a wall with a vertical forward wall of the housing being exposed to air space to be heated by the furnace and such forward wall being provided with openings affording air circulation between the interior of the housing and the air space, such wall furnace including a burner within and adjacent the bottom of the housing together with heat exchanger means in the housing for conducting combustion products to a chimney connection conduit; wherein such conventional type wall furnace is improved by the heat exchanger means being comprised of front and rear heat exchanger units, said front unit comprising an upstanding front casing including rectangular front, rear and top walls and tapered side walls defining a front chamber communicating with the interior of the housing, said rear casing being rectangular in horizontal section throughout its vertical extent with the vertical extent of the rear casing being substantially greater than the greatest horizontal extent thereof, the front wall of the rear casing being spaced rearwardly of the rear wall of the front casing and in substantial parallelism therewith, the rear wall of the rear casing being vertical whereby said rear casing is downwardly tapered, said rear casing being provided with an internal partition between the side walls thereof, said partition extending between the front and rear walls of the rear casing downwardly from the top wall thereof to terminate in a lower edge that is spaced about the lowermost extents of the front and rear walls thereof whereby the upper part of the rear chamber is laterally separated into first and second chamber portions, at least one of the last mentioned chambers being provided with rear unit baflle means for deflecting combustion products moving vertically therethrough alternately toward the front and rear walls of the rear casing, a transfer conduit connected between the upper ends of the casings and establishing communication between the upper ends of the front chamber and the upper end of the first chamber portion of the rear chamber, and said chimney connection conduit being connected to the upper end of the rear casing and establishing communication with the upper end of the second chamber portion of the rear chamber, whereby combustion products from the burner pass sequentially upwardly through the front chamber, the transfer conduit, downwardly through the first chamber portion, upwardly through the second chamber portion, and exit from the furnace through the chimney connection conduit.

A more limited aspect of the invention involves the provision of a shield interposed and spaced between the adjacent sloping sides of the front and rear casings to facilitate imparting a forward component of movement of heated air rising through the furnace and in order to obstruct direct exposure of the rear casing from radiant energy emanating from the front casing.

Still another more limited but important aspect of the invention involves the baflle means provided within the front casing being an integral structure which is removably received and detachably secured within the front casing.

An important feature of the present invention resides in the partitioning of all of the interior of the rear casing chamber except only the lowermost portion thereof into lateral chambers, and the internal bafiling of such two partitioned chambers and the opening of the lower end of the rear casing, whereby not only is efficient heat exchange obtained, but additionally an equalizing or stabilizing of the burner draft is realized, and also fewer bafile plates are required than would be the case if the rear chamber were partitioned into front and rear portions.

Another feature of the invention of considerable importance resides in the provision of a unitary or integral baffle means comprised of a pair of elongated members which are connected by a series of baffle plates extending therebetween, whereby such integral structure can be installed in or removed from the front casing as a unit to the end result that deterioration of the baffle means does not necessitate replacement of the entire front casing inclusive of the 'haflle means, it being noted that the baffle means are subjected to the most hostile environment of the entire equipment.

A final feature of the invention of importance to be specifically set forth resides in the provision of a shield intermediate the front and rear casings, such shield serving to augment imparting a forward component of motion to air circulating through the heat exchangers by convection and also serving to contact the rear heat exchanger unit through which relatively cooler combustion products are moving with relatively cooler air, and additionally serving to minimize heating of the rear casing by direct radiant energy emanating from the relatively higher temperature front casing.

These and other objects, aspects and features of the invention will manifest themselves in the following description of a preferred embodiment of the invention, such description to be taken in conjunction with the accompanying drawings illustrative of such embodiment, wherein:

FIGURE 1 is an isometric view of the front side of the wall furnace as the latter appears installed in a fragmentarily shown wall;

FIGURE 2 is a vertical sectional view of the wall furnace, this view being taken upon a vertical plane normal to the plane of the front of the wall furnace at the position indicated by the section line 2-2 in FIGURE 1;

FIGURE 3 is an isometric view of the rear heat exchanger casing with a portion of the front wall thereof being shown broken away to expose the partitioning and baffling therein, and wherein the tortuous path of combustion products therethrough is indicated by arrows;

FIGURE 4 is an isometric view of the front heat exchanger casing with a portion of the front wall thereof being shown broken away, and with the baffle means associated with such front heat exchanger casing being shown as partially withdrawn through the open lower end of such casing; and,

FIGURE 5 is a horizontal sectional view taken upon the plane of the section line 5--5 in FIGURE 2.

Referring now to the drawings wherein like numerals designate like parts throughout the various views, the reference numeral designates the wall furnace generally. The wall furnace 10 comprises a housing designated generally at 12 which includes a vertical rectangular rear wall 14, a horizontal rectangular top wall 16 and vertical rectangular side walls 18 and 20. The housing 12 also includes a forward or front vertical wall of generally rectangular configuration 22.

The front wall 22 is of somewhat greater vertical height than the rear and side walls 14 and 18 and 20 so as to extend below the rear and side walls 14, 18 and 20. The front wall is of a greater width than the spacing of the housing side walls 18 and 20, and the lateral vertical edges of the forward or front wall 22 are provided with integral rearwardly extending flanges 24 and 26 which are spaced on the opposite sides of the side walls 18 and 20 and which partially overlap a portion of the forward and rearward extent of the side walls 18 and 20. The rearmost vertical edges of the flanges 24 and 26 are inturned as indicated respectively at 28 and 30 to engage the outer surfaces of the side walls 18 and 20.

To limit heat transfer through the side walls 18 and 20 to the building wall 32 in which the furnace 10 is mounted, the side walls 18 and 20 are of such construction as to define air spaces therein as now to be described. The rear wall 14 and the side walls 18 and 20 are formed of sheet steel (preferably formed of sheet stock by bending at the junctures of the rear wall 14 with the side walls 18 and 20), and to establish the air spaces in connection with the side walls 18 and '20 referred to previously, a sheet steel panel 34 is disposed on the inner side and spaced from the side wall 18 to define an air space 36, the rear edge margin of the panel 34 being bent to define a flange 38 that is seated against and spot welded to the inner side of the rear wall 14. The forward edge margin of the panel 34 is bent into the form of an L-shaped flange 40 that is seated against and spot welded to the inner side of the side wall 18 at a position spaced rearwardly of the forward vertical edge of the side wall 18. The structure for defining an air space in association with the side wall 20 is similar to that just described in connection with the side wall 18 and includes a sheet steel panel 42 spaced inwardly from the side wall 20 to define an air space 44 therebetween, the rear and front vertical edges of the panel 42 being secured to the rear wall 14 and the side wall 20 at 46 and 48, respectively.

The front wall of the housing 12 is provided with a pair of rearwardly extending ribs or mounting plates 50 and 52 which extend rearwardly therefrom and which extend substantially the entire vertical height of the front or forward wall 22. The spacing of the ribs or mounting plates 50 and 52 is such that they are closely received between and overlap for a short interval the forward edge margins of the panels 34 and 42. The front or forward wall 22 of the housing 12 and the structure fixed thereto ( flanges 24 and 26, and ribs 50 and 52) are detachably secured to the side walls 18 and 20, and the panels 34 and 42 by means of sheet metal screws 53 extending through the overlapping and abutting portions of the ribs 50 and 52, and the panels 34 and 42. Means whereby access is had to such sheet metal screws will presently be described.

The front or forward wall of the housing 12 is generally conventional in that the same is provided with enlarged rectangular upper and lower openings 54 and 56 which are horizontally located intermediate the positions occupied by the ribs 50 and 52, and such enlarged rectangular openings 54 and 56 are normally closed by louvered doors 58 and 60, respectively. The louvered doors 58 and 60 are conventional and are conventionally mounted for hinging or swinging movement about vertical axes along the lefthand edges thereof as viewed in FIG- URE 1. The hinge means and the means for releasably holding the doors 58 and 60 in their illustrated closed positions are not exposed to view in the drawings; however, illustration and detailed description thereof is not seen to be necessary in view of the common employment of such means and as such structure will be abundantly clear to those familiar with the wall furnace art. Suflice to say, the doors 58 and 60 are louvered (that is, they have a plurality of upwardly and rearwardly inclined slots therethrough) whereby convection air currents induced by operation of the furnace 10 may freely enter and leave the housing 12 from the air space of the room to be heated by the furnace 10, and access to the interior of the housing 12 and to the previously mentioned sheet metal screws can be obtained on opening the doors 58 and 60.

The front or forward wall 22 and the flanges 24 and 26 as well as the doors 58 and 60 are fabricated of sheet metal. Preferably the external surfaces of the front wall 22, the flanges 24 and 26, and the doors '8 and 60 that are exposed to view from the room to be heated by the furnace are coated with a heat resistant enamel or the like so as to present a decorative appearance.

The upper edge of the front or forward wall 22 is spaced forwardly of the forward edge of the top wall 16 of the housing 12 as well as forwardly of the forward surface of the room wall 32, the arrangement being such as to define an opening or passageway 62 facing upwardly that is disposed forwardly of the plane of the wall of the room. A mounting flange or fitting -64 is secured to the top wall 16 of the housing 12 and is secured to the room wall 32. The fitting 64 is of such a configuration as to confine the movement of air upwardly from within the housing 12 through the opening to be such as to enter the room partially bounded by the room wall 32; whereby heated air does not pass from within the housing 12 to any hollow spaces within the room wall 32.

Aside from mentioning that the inturned edges '28 and 30 of the front wall flanges 24 and 26 seat against the inner surface of the building or room wall 32 when the furnace 10 is mounted so as to present a neat appearance, no detailed description of the means whereby the furnace 10 is attached to or mounted in the wall 32 is given for the reason that such structure is well known and the use thereof is commonly practiced by those in the wall furnace art. However, it is also to be noted that the wall furnace 10 is not only well suited for mounting between the studs forming a part of interior as 'well as exterior walls of fixed or permanently situated housing, but because of the substantial reduction in front to rear dimensions obtainable through the practice of this invention, the furnace 10 can be employed and perhaps will find proportionately greater employment in conjunction with positioning in the exterior walls of mobile homes, trailers and the like.

Disposed within the housing 12 in spaced relation to each other as well as in spaced relation to the rear wall 14, the top wall 16, the forward wall 22 and the panels 34 and 42 of the housing 12 are front and rear heat exchange units designated generally respectively by the reference numerals 66 and 68. The front heat exchange unit 66 comprises a front casing 78 comprised of a vertical rectangular front wall 70 and a rectangular rear wall 72 that is spaced rearwardly of the front wall and which is upwardly and forwardly inclined throughout its extent whereby the casing 70 is upwardly tapered in its forward and rearward horizontal dimension throughout its vertical extent, that is, the fore and aft horizontal dimension of the casing 78 progressively diminishes from the bottom to the top thereof. The causing 78 additionally includes tapered side walls 73 and 74 that extend between the lateral edges of the front and rear walls 70 and 72, and the upper end of the casing 78 is closed by a rectangular top wall 76. Thus the front casing 78 defines an upwardly tapering internal chamber 80 that is open at the lower major end 82 of the casing 78 so as to communicate with the interior of the housing 12 that is ambient to the front heat exchanger 66, it being noted that the lower end 82 of the casing 78 is spaced above the horizontal plane 83 defined at the lower edges of the side walls 18 and and the rear wall 14 of the housing 12.

A conventional fluid fuel burner 84 is disposed in vertical alignment with the open lower end of the chamber 80, and preferably at a height such as to be at least partially received within the chamber 80, though such height positioning is not essential as will be appreciated by those skilled in the art as it is only necessary that the burner 84 be disposed so that combustion products rising from the burner 84 be inducted or collected in their entirety within the chamber 80 for upward movement therethrough. As readily apparent upon inspection of FIGURE 2, the fore and aft horizontal dimension of the burner 84 is less, preferably substantially less, than the corresponding spacing of the lower ends of the front and rear walls 70 and 72. The lateral dimension of the burner 84, that is the dimension of the burner 84 perpendicular to the showing thereof in FIGURE 2, is the greatest horizontal dimension of the burner 84 and such dimension is less than but preferably constitutes a major proportion of the spacing between the tapered side walls 73 and 74 of the casing 78. Preferably, the burner 84 is of the type customarily used for the burning of natural gas or LPG, but as will be understood by those conversant with furnace burners the use of a burner suitable for combustion of liquid fuels is not precluded.

Inasmuch as the burner 84 and its associated fuel supply conduits, pressure regulators, control valves and the like are entirely conventional, and do not in themselves constitute inventive subject matter per se, the illustration and description thereof is omitted as the same would serve no useful purpose, be unnecessary to enabling those with ordinary skill in the art to practice the invention, and on the contrary would merely serve to obscure the actual invention.

The rear heat exchanger unit 68 includes a casing designated generally at 86 which is comprised of a rectangular vertical rear wall 88 that is parallel to and spaced from the rear wall 14 of the housing 12, and a rectangular upwardly and forwardly inclined front wall 90 that is spaced from and parallel to the rear wall 72 of the casing 78. The rear casing 86 includes tapered side walls 92 and 94 that are respectively coplanar with the previously described side walls 73 and 74, the side walls 92 and 94 being vertical and lying in planes perpendicular to the vertical plane of the rear wall 14 of the housing 12. The rear casing 86 additionally includes a rectangular horizontal top wall 96 that is substantially coplanar with the top wall 76 of the front casing 78.

It will thus be seen that the rear casing 86 defines an internal chamber 98 that is downwardly tapered in its front to rear dimension, and such chamber 98 is open at its lower end 100 at a vertical position preferably spaced above the vertical position occupied by the lower end 82 of the front casing 78.

As best shown in FIGURE 3 the rear casing 86 is provided with an internal partition wall 102 that divides all except the lowermost portion of the chamber 98 into lateral chamber portions 104 and 106 separated by the partition wall 102. The partition wall 102 is spaced intermediate and parallel to the tapered side walls 92 and 94 and extends downwardly from the top wall 96 and between the front and rear walls 90 and 88 to terminate in a lower end 108 that is spaced above the lower end 100 of the chamber 98.

A steel circular pipe 110 extends through aligned circular openings in the rear and front walls 72 and 90 of the front and rear casings 78 and 86, respectively, to provide communication between the upper end portion of the front casing chamber 80 and the upper end portion of the lateral chamber portion 104 of the rear casing 86. As will be evident upon inspection of the drawings, the pipe 110 is horizontal, disposed adjacent the upper ends of the casings 78 and 86, and is disposed to be perpendicular to the plane of the rear wall 14 of the housing 12. Furthermore, it will be noted that the pipe 110 is disposed laterally so as to open into the chamber 104 of the rear casing 86 at a position intermediate the side wall 92 and the partition wall 102.

Conventional means are provided (welded preferably or tight press fits) to alford effective sealing between the junctures of the exterior of the pipe 110 with the walls 72 and 90.

A vertical steel pipe 112 constituting a flue pipe or chimney connection is disposed to extend vertically through aligned openings in the top wall 16 of the housing 12 and the top wall 96 of the rear casing 86, it being noted that the pipe 112 is laterally disposed to open into the chamber 98 at a position intermediate the side wall 94 and the vertical partition wall 102. As in the case of the pipe 110,

suitable conventional means are provided to effect a seal between the exterior of the pipe 112 with the top wall 86 through which it extends. Preferably also, the juncture of the pipe 112 with the top wall 16 is sealed, but in any event it is preferred that the pipe 112 is snugly received through the opening in the top wall 16 provided therefor. It will be understood by those skilled in the art that the upper end of the pipe 112 is to be connected to an upstanding chimney for the purpose of enhancing the draft provided for the burner 84 and also for disposing safely of combustion products externally of the structure to be heated by the furnace 10.

As thus far described it will be appreciated that communication is established for combustion products produced in the vicinity of the burner 84 to the chimney connection pipe 112 along a path which sequentially includes upward passage through the chamber 80, horizontal passage through the pipe 110, downward passage through the lateral chamber portion 104, and finally upward passage through the lateral chamber portion 106 to the chimney pipe connection 112.

In order to effect an efficient heat transfer between hot combustion products rising through the chamber 80 with the front and rear walls 70 and 72 of the casing 78, a baffle means 130 is provided for alternately directing the movement of such rising gaseous combustion products forwardly and rearwardly against the front and rear walls 70 and 72. Such baffle means take the form of a pair of elongated steel strips 116 and 118 which support and are connected by two interdigitated sets of substantially horizontal bafiie plates 120 and 122. The vertical series or set of bafiie plates 120 may be considered the forward baffle set in that the forward edges of the baffle plates constituting such set terminate in relatively close proximity, if not in actual direct contact with the front wall 70 of the casing 78, with the rear edges of the baflie plates constituting the forward bafile plate set 120 terminating in uniformly spaced relation with the rear wall 72 of the casing 78. In other words, combustion products rising through the chamber 80 must pass in their substantial entirety between the rear edges of the baffle plates constituting the set 120 thereof and the rear Wall 72, with relatively little, if any, of such combustion products rising between the forward edges of such baffle plates and the front wall 70. The lateral extent of the baffle plates of both the series 120 and 122 thereof is only slightly less than the spacing intermediate the side walls 72 and 74, whereby the outer sides of the steel strips 116 and 118 have a sliding fit within the casing 78. In this regard it will be noted that the lateral extremities of all the bafiie plates are upturned as indicated at 124 and 126, and such upturned edges abut the adjacent sides of the strips 116 and 118 and are secured thereto, preferably by spot welding.

All of the baflie plates constituting the rear set 122 thereof overlap in horizontal projection the baffle plates of the forward set 120, and the rear edges of each of the baffle plates of the rear set 122 thereof terminate in close proximity to, if not in direct engagement with, the rear wall 72, and have their forward edges uniformly spaced from the front wall 70, the arrangement being such that virtually all of the combustion products passing upwardly by each of such baffie plates is constrained to pass forwardly thereof.

The baffle means structure 130 comprised of the previously described strips 116 and 118, and the baffle plates of the two sets 120 and 122 is slidably received within the casing 78 through the open lower end thereof. The baflie structure 130 is removably secured in the position shown thereof in FIGURE 2 by means of sheet metal screws extending through the lower end portions of the strips 116 and 118 and the side walls 73 and 74, it being noted that the previously described positions of the forward and rear edges of the baffie plate sets 120 and 122 respectively serve to properly locate the batile means 130 within the casing 78.

The baffle means 130 greatly improves the heat exchange efficiency of the heat exchanger unit 66 in that the hot combustion products are not allowed to flow upwardly through the casing 78 in a manner even remotely similar to what might be termed laminar flow, that is, that portion of the combustion products near the fore and aft center of the casing 78 moving upwardly through the casing in such a manner as to remain essentially so centered and therefore being relatively uncooled by the front and rear Walls 70 and 72 as compared to combustion products progressing upwardly more or less continuously in contact with such walls. In other words the rising combustion products are caused to undergo a substantial degree of alternate fore and aft shifting in the direction of movement so that the hottest portions of such combustion products are continuously brought into engagement alternately with the front and rear walls 70 and 72 for efficient transfer of heat thereto. Inasmuch as the baffle means are subjected to the most deleterious environment to which any of the heat exchanger structure is subjected, such baffle means 130 notwithstanding being constructed of durable materials may eventually need replacement. Construction of the bafiie means 130 as an integral structure removably secured in the casing 78 permits replacement of the bafile means 130 without any need for replacement of the entire front heat exchanger unit 66. This substantial advantage is in addition to the advantage of the economy realized by fabricating the baffle means 130 as a unit for subsequent assembly with the casing 78.

The rear casing 86 is provided with bafiie means disposed in each of the chamber portions 104 and 106 thereof to prevent anything remotely approaching laminar flow of combustion products through the chamber portions 104 and 106 and to substantially enhance the efficiency of the heat exchange effected by the heat exchanger 68. Inasmuch as the combustion products entering the casing 86 from the pipe 110 are substantially cooler than those passing upwardly in the lower portion of the front chamber 80, the baffle means can be made integral with or permanently attached to the casing 86.

The baffle means provided in the chamber 106 comprises a vertical series or rear set of baflle plates 136 each of which includes, as in the case of the bafile plate indicated at 138, a horizontal portion 140 extending forwardly from the rear wall 88 to terminate in an edge spaced from the front wall 90. The baffle plate portion 140 is horizontal and extends laterally from the side wall 94 to the partition 182. The bafiie plate 138 is downturned at its juncture with the rear wall 88 and is suitably secured thereto as by spot-welding at 142. Each of the baffle plates of the series 136 terminate at their forward edges with a uniform extent of spacing from the front wall 90. The baffle means in the chamber 106 includes a second set of bafiie plates 144 which are mounted upon the front wall 90. The baffle plates comprising the set thereof 144 are vertically spaced and interdigitated with the baffle plates of the set 136. Each of the baffle plates of the series or set 144 thereof is horizontal, extends between the side wall 94 and the partition 102, and extends horizontally from the front wall 90 to terminate in spaced relation with respect to the rear wall 88. As will be seen upon inspection of FIGURE 2, the horizontal extents of the baffle plates of the two series of bafiie plates 136 and 144 overlap each other as to their horizontal projection, and as in the case of the baffle plates of the series 136, the baffie plates of the series 144 terminate with a uniform degree of spacing from the rear wall 88.

The compartment 104 has baflie means identical to the bafiie means previously described in connection with the chamber 106 and such baffie means includes a rear series of bathe plates that correspond to the previously described series of baffle plates 136, and a front series of baffle plates 152 that correspond to the previously described series of baffle plates 144. The bafile plates of the series 158 and 152 extend between the side Wall 92 and the partition 102, and may be considered as horizontal extensions of the baffle plates disposed in the chamber 106, merely being disposed on the opposite side of the partition wall 102. It will be obvious that the baffle plates disposed in the chamber 104 can be vertically staggered with respect to the baflie plates in the chamber 106 if desired or deemed expedient, as they need not be arranged so as to effectively constitute horizontal extensions of each other.

As thus far described, it will be appreciated that combustion products which rise to the upper portion of the chamber 80 of the casing 78 pass into the upper part of the chamber 104 through the pipe 110, and such combustion products thence pass downwardly through the chamber 104 pursuing a to-and-fro course in the forward and rear direction so as to intimately contact the rear and front walls 88 and 90 of the casing 86 as indicated by the flow arrows 160, and such combustion products pass into the region of the casing chamber 98 disposed below the lower end 108 of the partition wall 102 and in such region turn upwardly as indicated by the flow arrow at 162 to enter the lower end of the chamber 106 to thence proceed upwardly with a forwardly and rearwardly toand-fro movement as indicated by the flow arrows 164 to the upper end of the chamber 106 from which the combustion products exit by the chimney connection pipe 112.

The combustion products flowing from the burner 84- pursue the course described by virtue of the draft or pressure differentials resulting from the substantially lower densities of the hot combustion products as compared to densities of air ambient to the furnace 10. The lesser density of the warm or hot combustion products directly contributes to the upward movement of the combustion products through the casing 78 and through the chamber portion 106 of the casing 86, with the downward movement of the combustion products through the chamber portion 104 resulting from the draft effects or buoyancy of the combustion products in the chamber 106 and also being forced by the relatively greater buoyancy of the combustion products in the casing 78 as compared to the relatively lower buoyancy of the lower temperature combustion products in the chamber portion 104.

Recalling that the lower end of the casing 86 is open, the rate of movement of combustion products upwardly through the front casing 78 and consequently the rate of movement of air upwardly into the lower end of the casing 78 is maintained relatively constant or stabilized by virtue of the lower end of the casing 86 being open. Ordinarily, rather large magnitude fluctuations in such combustion product and air flow result from the upper end of the chimney to which the connector pipe 112 is connected being subjected to wind gusts and turbulent air flow; however, the provision of the baflle means in the chamber portion 106 tends, in and of itself, to dampen or smooth out such variations in movement of combustion products through the chamber 106 and consequently subject the lower end of the chamber 104 to a more uniform draw or suction. The draw or partial suction to which the lower end of the chamber 104 is maintained even of greater constancy by virtue of the communication afforded between the lower end of the chamber 98 and the air ambient to the casing 86. For example, if a wind gust or turbulent air flow is such as would tend to substantially reduce the pressure at the lower end of the chamber portion 106, such reduction in pressure is minimized inasmuch as air can enter the lower open end of the casing 86 to reduce any such reduction in pressure that would otherwise occur. Such stabilization or maintenance of substantially constant pressure at the lower end of the chamber 98 obviously tends in turn to stabilize the rate of flow of combustion products through the chamber portion 104. The advantages flowing from such equalized or stabilized flow of combustion products (which stabilization or equalization of flow rates has been repeatedly verified and confirmed in tests made with an actual working model employed under extreme environmental conditions) are such that a more uniform and complete combustion of fuel is realized so as to obtain a more eflicient conversion of chemical energy to heat energy, and in that a quieter burning of fuel is effected, it being noted that when the flow rates of air and combustion products about a burner are unstable and fluctuate wildly that there are substantial intensities of noise generated.

The heat exchanger casings 78 and 86 are formed of aluminized sheet steel of the type customarily employed in gas furnaces and particularly such portions thereof that enclose combustion chambers. Inasmuch :as the heat exchanger casing 86 is subjected to lower temperatures than the casing 78, the former can be constructed of sheet steel of lesser thickness if desired. It has been determined from utilization of the working model of the invention alluded to previously that the casing 78 can be made of 22 gauge sheet steel, with such joints which may be necessarily made during the fabrication thereof being in the form of overlapping joints that are spot welded. The rear casing 88 is preferably also fabricated of 22 gauge sheet steel in the same manner as the front casing 781. Stainless steel can be used if desired, but aluminized sheet steel is deemed preferable because of excellent heat transfer and thermal radiation characteristics.

The baffle means 130 are fabricated in their entirety of stainless steel of 22 gauge, however, greater thickness stock can be employed for larger furnaces if deemed necessary. In lieu of using greater thickness stainless steel, or in addition to using greater thickness stainless steel, the baffle plates can be such as to be of a very shallow V- shape in vertical transverse section so as to impart a greater strength or stiffness to the same, it being understood that in use that at least the lowermost of the baffle plates will be at a very high temperature during furnace operation and will at least be cherry red. It has been found that not only do the baffle plates of the baffle means 130 greatly enhance the heat exchange efficiency, such baflle means 130 contributes substantially to the efiiciency of combustion and serves to reduce the amount of carbon monoxide contained in the combustion products. It is believed that the intimate contact of the unburned portions of the fuel that may be contained with the hot combustion products are largely caused also to oxidize along with carbon monoxide present by virtue of the intimate contact obtained with the hot baffle plates.

Extensive experiments made with the working model referred to previously show that a spectacular improvement in the operation of the furnace 10 is obtained when the baffle means 130 are employed as compared to the results obtained when the baffle means 130 are removed. For example, with the baflie means 130 removed, it has been found that the midstream temperature of combustion products passing through the pipe is in the range of 700 to 800 degrees Fahrenheit, whereas with the baffle means installed and all other conditions being unchanged, the midstream temperature of combustion products passing through the pipe 110 are within the temperature range of 300400 degrees Fahrenheit. As might be expected, the temperatures of the lower portions of the walls 70 and 72 of the casing 78 are in the lower portion of their extents much higher when the baffle means 130 is employed than is otherwise the case. As a matter of fact it has been found that in the tests made with respect to the working model that the external temperature of the upper end extremities of the walls 70 and 72 are about the same whether the baflle means 130 are installed or not, but that a much steeper temperature gradient exists progressively downwardly along the extents of the walls 70 and 72 when the baflle means 130 is installed than occurs when the baffle means 130 are not employed.

The tests also indicate that the midstream temperature of combustion products passing upwardly through the pipe 112 is about 250 F. when the bafile means 130 are not employed, whereas such temperature is about 120 F. when the baffle means 130 are employed.

The latter mentioned temperature tests indicate a very substantial reduction in the amount of heat lost up through the chimney when the baflle means 130 are employed. The employment of the baffle means 130 actually results in greater savings with respect to heat lost up through the chimney pipe 112 than appear to be indicated by the temperature measurements described above in that the flow rate of gases upwardly through the chimney connection pipe 112 is considerably less when the baffle means 130 are employed than when they are not employed.

In the preferred construction of the furnace and in order to improve the heat exchange efficiency of the heat exchangers 66 and 68, a generally rectangular shield 170 is interposed in spaced relation between the heat exchanger Walls 72 and 9f), the shield 170 being parallel to such walls and physically approximately of the same dimensions as the Wall 72 of the casing 78. The shield 170 is of a U-shaped or channel cross section with the legs 172 thereof projecting toward the casing 78 from the web portion 174 of such U-shaped shield.

The shield 170 can conveniently be fabricated from 22 gauge sheet steel. The shield 170 serves to obstruct or prevent thermal radiation from the wall 72 from proceeding directly to the wall 90 of the rear heat exchanger. Furthermore, the shield 170 serves to define and separate front and rear 176 and 178 convection zones from each other, it being noted that such zones 176 and 178 are upwardly and forwardly inclined so that air rising in such zones by virtue of having been reduced in density by receiving or accepting heat from the heat exchangers has a forward direction component of movement imparted thereto, and it will be noted that such direction of move ment is such as to be directed substantially straight to- Ward the open space in the housing defined intermediate the upper front edge of the forward wall 22 of the housing 12 and the building wall 32.

It is highly desirable that the front and rear zones 176 and 178 tend to remain separated for the reason that the air moving upward through the rear zone 178 will be relatively cooler than the air moving up through the zone 176 whereby a more efficient heat exchange will be realized for the rear heat exchanger 68. In other words, the relatively cooler combustion products in the rear heat exchanger 68 will be in heat exchange relation with relatively cooler air circulating thereby.

It will be noted that the web portion 176 of the shield 170 is provided with an opening therethrough to accommodate the pipe 110 therethrough.

A deflection plate 180 is mounted on the top of the rear heat exchanger 68, such deflection plate 181) projecting upwardly and forwardly into space intermediate the upper end of the zone 178 and the top wall 16 of the housing 12, such deflection plate 180 further contributing to deflection of rising and heated air outwardly from within the housing -12 into the space to be heated. Furthermore, the deflection plate 180, being so disposed with respect to the zone 178 is believed to enhance or facilitate the movement of air rising upwardly between the rear wall 88 of the casing 86 and the rear wall 14 of the housing 12 in its passage from within the upper end of the housing 12 to the space to be heated by the furnace 10.

Although not shown in the drawings, it will be understood that the casings 78 and 86 as well as the shield 170 are supported in the positions shown thereof in the drawings by means of brackets carried by the panels 34 and 42 of the housing 12.

Although the illustrated embodiment of the invention has been described in elaborate detail, it is to be emphasized that such detail is for the purpose of assuring a full and complete understanding of the principles involved, and no inference of narrowness of scope of invention is to be drawn. Indeed, it is thought evident susceptible to numerous and various changes and modifications without departing from the spirit of the invention, and accordingly, reference is directed to the appended claims in order to ascertain the actual scope of the invention.

I Claim:

1. In a wall furnace of the type including an upstanding generally rectangular housing adapted for positioning in a wall with a vertical forward wall thereof being exposed to air space to be heated by the furnace and such forward wall being provided with openings affording air circulation between the interior of the housing and the air space, said wall furnace including a burner within and adjacent the bottom of the housing together with heat exchanger means in the housing for conducting combustion products to a chimney connection conduit; the improvement therein of said heat exchanger means comprising front and rear heat exchanger units, said front unit comprising an upstanding front casing including rectangular front, rear and top walls and tapered side walls defining a front chamber communicating with the interior of the housing through the bottom of the front casing, said front casing being rectangular in horizontal section throughout its vertical extent with the vertical extent of the front casing being substantially greater than the greatest horizontal extent thereof, the front wall of the front casing being parallel to and spaced from the forward wall of the housing with the rear wall of the front casing being upwardly and forwardly inclined, whereby said front casing is upwardly tapered, said burner being disposed adjacent the open lower end of the front chamber, said first casing being provided with front unit baffle plate means therein for deflecting combustion products rising therethrough alternately toward the front wall and the rear wall of the front casing, said rear heat exchange unit comprising an upstanding rear casing including rectangular front, rear and top walls and tapered side walls defining a rear chamber communicating with the interior of the housing, said rear casing being rectangular in horizontal section throughout its vertical extent with the vertical extent of the rear casing being substantially greater than the greatest horizontal extent thereof, the front wall of the rear casing being spaced rearwardly of the rear Wall of the front casing and in substantial parallelism therewith, the rear wall of the rear casing being vertical whereby said rear casing is downwardly tapered, said rear casing being provided with an internal partition between the side walls thereof, said partition extending between the front and rear walls of the rear casing downwardly from the top wall thereof to terminate in a lower edge that is spaced about the lowermost extents of the front and rear walls thereof whereby the upper part of the rear chamber is laterally separated into first and second chamber portions, at least one of the last mentioned chambers being provided with rear unit baflle means for deflecting combustion products moving vertically therethrough alternately toward the front and rear walls of the rear casing, a transfer conduit connected between the upper ends of the cas- 1ngs and establishing communication between the upper ends of the front chamber and the upper end of the first chamber portion of the rear chamber, and said chimney connection conduit being connected to the upper end of the rear casing and establishing communication with the upper end of the second chamber portion of the rear chamber, whereby combustion products from the burner pass sequentially upwardly through the front chamber, the transfer conduit, downwardly through the first chamber portion, upwardly through the second chamber portron, and exit from the furnace through the chimney connectlon conduit.

2. The combination of claim 1, wherein said rear unit baffle means is provided for both the first and second chamber portions.

3. The combination of claim 1, wherein the front end rear casings are substantially coextensive vertically.

4. The combination of claim 3, wherein the lower end of the rear casing is spaced above the lower end of the front casing.

5. The combination of claim 1, wherein the front unit baffle means is removably received as an integral structure within the front chamber through the open lower end of the latter, such structure comprising a pair of elongated and spaced parallel frame members, a series of vertically spaced elongated baffle plates extending between and connected to said members, said vertical series of baffle plates being comprised of interdigitated first and second sets of baffle plates with the baffle plates of the first set thereof having front and rear edges that are relatively near to and remote from the front and rear walls of the front casing respectively, and with the baflle plates of the second set thereof having rear and front edges that are rela tively near to and remote from the front and rear walls of the front casing respectively.

6. The combination of claim 1, including a rectangular shield spaced intermediate and parallel to the rear and front walls of the front and rear casings respectively, whereby upwardly and forwardly directed forward and rear convection zones are established on opposite sides of the shield with the latter obstructing direct exposure of the rear casing to radiant energy emanating from the front casing.

7. The combination of claim 7, wherein the shield is U-shaped in horizontal section to include forwardly extending legs connected by a web, whereby the forward convection zone is at least partially isolated from the rear zone.

8. The combination of claim 1, wherein said rear baflle means comprises a first series of vertically spaced baffle plates each having forward edges secured to front wall of the rear casing, and a second series of vertically spaced baflle plates each having rear edges secured to the rear wall and front edges spaced from the front wall of the rear casing, with the baffle plates of the first and second series thereof being interdigitated and vertically spaced with respect to each other.

9. The combination of claim 8, wherein the front baflie means is removably received within and detachably secured to the front casing as an integral structure that is comprised of a pair of parallel elongated members and a series of vertically spaced bafile plates extending between and connecting said members, and said integral structure having an external configuration generally conformable to the front chamber.

10. The combination of claim 1, wherein said housing includes a rear wall and a top wall respectively spaced to the rear of the rear casing and above the front and rear casings, a rectangular shield spaced intermediate and in substantial parallelism to the rear and front walls of the front and rear casings respectively to define a pair of upwardly and forwardly inclined convection zones on opposite sides of the shield, and a deflection member carried at the top of the rear casing and projecting over at least one of the zones at a vertical position intermediate the upper end of the shield and the top wall of the housing.

References Cited UNITED STATES PATENTS 1,991,704 2/1935 Schellhammer et al. 126-116 2,090,053 8/1937 Kuenhold 126--116 2,818,059 12/1957 Cayet.

JAMES W. WESTHAVER, Primary Examiner.

US. Cl. X.R.

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