US3496927A

US3496927A - Sealed-combustion system and flue apparatus suitable for use therein

Info

Publication number: US3496927A
Application number: US761718A
Authority: US
Inventors: Douglas W De Werth; Richard M Oehlschlaeger
Original assignee: Dover Corp
Current assignee: Dover Corp
Priority date: 1968-09-23
Filing date: 1968-09-23
Publication date: 1970-02-24
Anticipated expiration: 1987-02-24

Description

Feb. 24, 1970 D. w. DE WERTH ET -COMBUSTION SYSTEM AND FLUE APPARAT SEALED Filed Sept. 23, 1968 SUITABLE FOR USE THEREIN 2 Sheets-Sheet 1 FIG. 2.

FIG. 7.

mvzm-oas: DOUGLAS W. DeWERTH B RICHARD M. OEHLSCHLAEGER Md Z5 //0 ATTYS.

Feb. 24, 1970 D. w. DE WERTH ET AL SEALED-COMBUSTION SYSTEM AND FLUE APPARATUS SUITABLE FOR USE THEREIN 2 Sheets-Sheet 2 Filed Sept. 23. 1968 mvcu'ronsz DOUG LAS W. DeWERTH RICHARD M.OEHLSCHLAEGER FIGS.

ATTYS.

United States Patent O 3,496,927 SEALED-COMBUSTION SYSTEM AND FLUE APPA- RATUS SUITABLE FOR USE THEREHN Douglas W. De Worth, Cleveland, and Richard M.

Oehlschlaeger, Novelty, Ohio, assignors to Peerless Manufacturing Division of Dover Corporation, Louisville, Ky., a corporation of Delaware Filed Sept. 23, 1968, Ser. No. 761,718

Int. Cl. F231 17/64 US. Cl. 126-85 15 Claims ABSTRACT OF THE DISCLOSURE A flue system for supplying combustion air from an inlet orifice at the outside of a building wall to a gas-fired furnace within the building and for returning flue gases from the furnace to a discharge orifice at the exterior of the building wall. The flue system fits between the studs in the building wall and is flush with the exterior of the wall. The discharge part of the system includes a vertical stack having a top Opening communicating with the discharge orifice by way of a discharge chamber and also having a lower opening communicating with ambient. The combustion-air intake portion of the system includes an inlet chamber supplied from the inlet orifice. Effects of wind incident on the inlet orifice and on the discharge orifice are reduced by shaping of the inlet and discharge chambers so as to reverse the air currents produced therein by incident wind, and to direct them outwardly. The desired flow of wind currents in the inlet chamber is enhanced by an angled deflector at the center of the exterior of the unit.

BACKGROUND OF THE INVENTION Sealed-combustion systems are known in which a combustible-fuel furnace in an enclosure is supplied with combustion air from outside the enclosure and in which gaseous products of combustion are vented or exhausted to the exterior of the enclosure. Ordinarily a natural convection flow of combustion air and flue gases is relied upon to provide the proper rate of supply of combustion air and the proper rate of venting without requiring forced-air draft.

One major problem in such systems lies in the interference with proper air and gas flow produced by wind incident on the inlet and vent orifices which communicate with the ambient air. In some instances the effects of wind are mitigated by use of baflles extending over the inlet and discharge orifices, which may for example be located on the roof of a building. However, such external baflles are unsightly and undesirably space-consuming, particularly if intake and venting is through a side wall of the building.

It is therefore desirable in many cases to provide flue apparatus for a sealed-combustion furnace, which flue apparatus terminates flush with the exterior of a building wall. In known systems of this type, long conduits have been required to decrease the inlet pressures in the presence of wind and to provide sufficient chimney effect to maintain flame stability and satisfactory combustion and thermal efficiency in the furnace. Such systems are less compact and less effective than is desirable for many purposes.

Accordingly, it is an object of the invention to provide new and useful apparatus for supplying combustion air to a furnace and for venting of exhaust gases therefrom.

Another object is to provide such apparatus which is compact, yet resistant to the interfering effects of wind on air and gas flow in the apparatus.

A further object is to provide such apparatus which ice can be mounted with its inlet and discharge orifices substantially flush with the outside of a wall where they are subject to incident wind without thereby rendering the air and gas flows to the furnace sensitive to the wind.

It is also an object to provide such apparatus which can be easily mounted in the wall of a building in the space between adjacent vertical studs in the wall.

SUMMARY OF THE INVENTION These and other objects of the invention are achieved by the provision of apparatus comprising a vent stack having a first opening for receiving flue gases from a combustion furnace, having a top opening for venting said flue gases therefrom, and having a lower opening communicating with ambient for enhancing the chimney effect in the stack and for mitigating the effects of wind on the desired flow. Preferably, the vent stack is proportioned to fit within the empty space in a building wall. A discharge chamber above the stack top opening is preferably employed, through which the flue products are vented to the discharge orifice, which is preferably flush with the exterior of the building wall; the discharge chamber is configured so that wind incident on the discharge orifice produces a reversed air flow outward across the top opening in the stack to prevent back pressures at the top opening. Preferably also, one or more inlet chambers are employed through each of which combustion air is supplied to the combustion air inlet of the furnace from a corresponding inlet orifice which also is preferably flush with the outside of the wall. Each inlet chamber is preferably configured to reverse air currents due to wind incident on the inlet orifice and thereby produce an outward flow of air therein for mitigating the effects of wind on combustion-air flow. Preferably also, an angled inlet deflector exposed to the ambient outside the wall is positioned to deflect wind currents into each inlet chamber in the direction to enhance the desired directions of air flow therein.

In the preferred embodiment, an air channel is provided across the top of the discharge chamber which communicates at one end with ambient outside the wall and at the other end with the inlet chambers, thereby to provide a cooling flow of air over the top of the discharge chamber. An outwardly-extending top deflector is preferably also positioned along the outer top edge of the discharge orifice to minimize heating of the superjacent wall by hot discharge gases. Also in the preferred embodiment, compactness is enhanced by a combination in which the angled inlet deflector is positioned along the outer side of the flue stack, said inlet chambers are positioned along both vertical edges of the stack, and the lower opening to the stack communicates with ambient through an orifice extending across the stack between the inlet orifices, the entire assembly, except for the protruding top deflector being mounted between the vertical studs within a building wall to provide combustion-air and flue exhaust for a furnace on the inner side of the wall.

While in the preferred embodiment all of the cooperating features of the system are employed together, some of the advantages of the invention may be realized by using less than all such features in a given application.

Other objects and features will be more readily understood from a consideration of the following detailed description, taken in connection with the accompanying drawings, in which:

FIGURE 1 is an elevational view, partly broken away, illustrating an application of the invention in which the flue system is built into the interior space in a building 'wall to supply combustion air to, and discharge flue gases from, a gas-fired wall heater;

FIGURE 2 is an elevational external view of the flue system employed in the application shown in FIGURE 1, to an enlarged scale;

FIGURE 3 is a sectional view taken along lines 3-3 of FIGURE 2;

FIGURE 4 is a top View, partly in section, of the flue system of FIGURE 2;

FIGURES 5 and 6 are front and rear perspective views, respectively, with parts broken away, of one of the two identical halves of the flue system of FIGURE 1; and

FIGURES 7 and 8 are schematic top and side views, respectively, of apparatus in accordance with the invention in which reference will be made in describing the flow of air and gases through the apparatus.

Referring now in detail to the embodiment of the invention shown in the drawings by way of example only, FIGURE 1 shows a building 10 having an exterior wall 12 comprising upright wooden studs such as 14, 16 (see FIGURE 2), outer sheathing 18 covering the outer surface of the studs, and inner sheathing 20 constituting the inner wall surface of the building. In building 10, and on the inner side of wall 12, there is located a gas-fired wall heater 24, comprising a combustion furnace in which gaseous fuel is burned to provide heating of the interior of the building. By means of the flue system 28 in wall 12, combustion air for the gas burners is drawn in from, and combustion gases are exhausted to, the ambient outside the building wall 12, rather than from and to the interior of the building. The structure of the preferred embodiment of the inventive flue system 28 will now be described in detail with particular reference to FIG- URES 2-6.

The flue system shown comprises a number of component parts which may be made of sheet metal and which, where not integrally formed, may be held together in any conventional manner as by welding or by fasteners for example, which are so well known as not to require specific showing or description. In this example it is assumed that the flue connections to the wall heater 24 are concentric and rectangular, and accordingly the discharge delivery conduit 30 for delivering exhaust gases from the furnace to the interior of the flue system 28 is a hollow rectangular duct and the combustion-air delivery conduit 32 for supplying combustion air to the wall heater 24 comprises a duct of rectangular cross-section concentric with and surrounding conduit 30.

Considering first the discharge or exhaust system for the combustion gases, the discharge delivery conduit 30 communicates with flue stack 36 through a rectangular opening 37 of the same size as the conduit 30. Opening 37 is centered laterally with respect to stack 36 and is positioned above the bottom of the stack. Flue stack 36 is in the form of a vertically-extending chamber of generallyrectangular cross-section, although the front face 38 thereof is modified in this example to provide an angled flow deflector for purposes stated hereinafter. Flue stack 36 is uncovered at its top to provide a top opening 39 coextensive with the cross-sectional dimension of the stack. The bottom of the flue stack 36 is closed, except for a lower opening 40 extending along the lower front edge of the stack below the area of connection to the discharge delivery conduit 30. The lower opening 40 in the stack communicates with the ambient on the outside of wall 12 by way of an inlet aperture 42 coextensive with lower opening 40 and covered by an expanded-metal screen 44 for protection against entry of foreign bodies of substantial size. Top opening 39 of stack 36 communicates with the discharge orifice 50, disposed flush with the exterior of wall 12, by way of a discharge chamber 52; orifice 50 is covered with an expanded-metal screen 54. A top deflector 58 extends outwardly and upwardly from the uper edge of discharge chamber 52 to minimize contact of the hot discharge gases with the exterior sheathing 18 of the wall 12. A heat-reflecting plate 60 is mounted above the top exterior surface of discharge chamber 52 by means of an appropriate bracket 62, to minimize transmission of heat from the discharge chamber to the wall structure.

As indicated by the stippled arrows in FIGURES 7 and 8, hot flue gases from the wall heater 24 move by convection flow through discharge delivery conduit 30 to flue stack 36, upwardly in the stack and through top opening 39 thereof, and thence outwardly to the exterior by way of discharge chamber 52 and discharge orifice 50, where they are de ected away from the building wall by the top deflector 58.

Lower opening 40 in flue stack 36 provides a number of functions. In the absence of substantial wind incident on the exterior of building wall 12, ambient air enters through lower opening 40 and is entrained with the rising flue gases so as to provide some degree of cooling thereof and corresponding mitigation in the heating effect of the flue gases on the building wall. In the presence of substantially equal forces of wind incident on the discharge orifice 50 and on the inlet aperture 42, the lower opening 40 serves to balance the effects of wind on the discharge orifice and to permit continuation of the normal discharge of combustion gases by flue effect substantially as in the absence of wind. In the presence of stronger winds at discharge orifice 50 than that at inlet aperture 42, or vice versa, the discharge orifice and the inlet aperture act as relief openings one for the other; this serves in effect to provide additional isolation of the discharge delivery conduit 30 from the effects of differential wind pressures which otherwise might produce substantial back pressures in the discharge delivery conduit, inadequate exhaust of combustion gases, and possible suffocation or extinction of the flame in the heater.

Discharge chamber 52 has horizontal top and bottom surfaces and a curved, substantially semi-cylindrical closed inner surface 63 joining its top and bottom surfaces at the opposite end from discharge orifice 50, so that wind entering the chamber near its top travels along and around the curved surface 63 beyond the top opening 39 in the stack 36 and is turned or reversed in direction so as to flow outwardly over the latter top opening, as shown for example in FIGURE 8 by the single-line arrows. The effect of wind in producing back pressure at top opening 39 is thereby automatically reduced. A lip 64 extending along the rear edge of the top opening 39 causes an upward jump in the reversed air flow so that wind in fact produces a negative pressure and some degree of aspiration of air from stack 36. The flow produced in the presence of wind is therefore such to assure that there will be no net back pressure on the top opening 39 which would interfere with proper exhaust of combustion gases.

Combustion air is supplied to combustion air delivery conduit 32 by convection flow from the pair of

generallyrectangular inlet orifices

70 and 72 flush with the exterior surface of wall 28 and covered by expanded-

metal screens

74 and 76. The general path of combustion air, as shown in FIGURE 7, is inward through

inlet orifices

70 and 72, then through inlet chambers 78 and 80-, respectively, and thence via a manifold 84 to the combustion-air delivery conduit 32. The general system is therefore of the so-called balanced flue type in that the effects of substantially equal winds incident on the discharge orifice and on the inlet orifices are automatically balanced out so as to provide substantially the same convection flow in the presence or absence of such winds. However, in the presence of various compositions, directions and differentials of wind incident on the inlet and discharge orifices, the

inlet chambers

78 and 80 provide significant improvements in flame stability, quality of combustion and thermal efliciency.

The two

inlet chambers

78 and 80 are mirror images of each other and hence only chamber 78 will be described in detail. Chamber 78 has parallel vertical sides adjacent the inlet orifice 70, but the interior rear surface of the chamber is curved in the form of a semi-cylinder, preferably with a radius somewhat larger than the width of the chamber adjacent the inlet orifice. In the absence of substantial wind, normal convection flow of ambient combustion air takes place through the inlet chamber. In the presence of strong wind incident on inlet orifice 70, a circulatory flow pattern is set up as represented by the arrows in FIGURE 7, in which the direction of flow is reversed and an outward flow of air produced across the inlet opening of manifold 84, thereby reducing the pressure and flow of combustion air in manifold 84 which would otherwise occur in response to wind.

In the preferred embodiment of the invention, the lower ends of the two

inlet chambers

70 and 72 are closed, but the top ends are open so as to communicate with a ventilating chamber 92 formed between the outer surface of discharge chamber 52 and a ventilating conduit wall 94 extending above, behind and laterally beyond the upper and rear outer surfaces of the discharge chamber. As indicated by the arrows in FIGURE 6 for example, ambient air is thereby enabled to flow by convection through the

inlet chambers

78 and 80, upward through the ventilating chamber 92, and outward through the ventilating exhaust orifice 96 and the screen 98 covering the orifice. This flow provides additional thermal isolation between the hot discharge chamber and the adjacent building structure.

The desired direction and nature of flow of air in the presence of wind in the

inlet chambers

78 and 80 is enhanced by the angled front deflector 100 comprising two

similar deflector panels

102 and 104 arranged in mirror image relationship and angled inwardly with respect to the wall 12 from a common vertical vertex axis 106. The sides of the

inlet chambers

78 and 80 are provided with screen-covered openings at 108 and 110* to permit entry of wind deflected radially outward from axis 106 into the two inlet chambers 78 and 80' at an angle transverse to the chambers, so as to assist in setting up the desired direction of flow around the rear interior portions of the respective chambers.

It is noted that the entire flue system is not only adapted to provide the desired mitigation of undesirable effects of incident wind as well as substantial thermal isolation from the supporting building structure, but is sufliciently narrow and of sufliciently small depth to be adapted for location entirely within the building wall, with the exception of the top deflector 58. Furthermore, the outer face area of the system is compact, with substantially all of the area presented to ambient being utilized to enhance operation. Because the flue system is located within a wall, it avoids the unsightly appearance of projecting baflle devices of the prior art, as well as their requirements for exterior space, and at the same time does not require substantial space, if any, within the enclosure of the building.

Without thereby in any way limiting the scope of the invention, the following specific example of materials and dimensions is given in the interest of complete definiteness with respect to one specific form which the system of the invention may take.

The walls of the building or enclosure in which the flue system is to be incorporated may be comprised of vertical two-by-four studs on 16 inch centers, with the flue system hung between a pair of adjacent studs, and between the inner and outer wall surfaces, by any appropriate mounting means such as the tab-and-

bracket arrangements

120 and 122 of FIGURE 2. The discharge delivery conduit 30 may be about 4 inches square, and the combustion-air delivery conduit 32 about 6- inches square and coaxial with the discharge delivery conduit. The flue stack 36 may be about 8 inches in horizontal width, about 11 inches high and about 1%. inches deep at its edges and 1% inches deep at its center. The inlet aperture 42 may be about one inch high, extending along the entire front of the stack. The

inlet chambers

70 and 72 may each be about 2 /2 inches in width and about 11 inches in height, with about 1 /8 inches of the outer edge of each chamber closed off by vertical strips. The overall depths of the' inlet chambers may be about 4 /2 inches, the interior curved surfaces such as 88 each having a radius of about 1% inches. The internal width of the manifold 84 may be about 1% inches. The discharge chamber 52 may be about 3 inches high and about 11 /2 inches long, with an internal radius at its inward end of about 1 /2 inches. The point at which the center of the discharge delivery conduit 3:!) enters the flue stack 36 may be about 4 /2 inches above the bottom of the flue stack. The width of the ventilating chamber may be about 13 inches and the radius of its interior rear portion about 2 inches. The ventilator discharge opening 96 may be about one inch in height. The top deflector 58 may be about 1 inches in width and about 13 inches in length, with an upward tilt such that its outer edge is about inch above its inner edge. If the top deflector is angled more sharply upward or downward its heat shielding effect may be reduced, and if it is angled substantially downward it may also present a restriction on the outward flow of exhaust gases, which is generally undesirable. The screening employed throughout may be expanded-metal with diamond-shaped apertures, the larger transverse dimension of which is about one inch and the smaller transverse dimension of which is about inch, the width of the screen material between the apertures being about .078 inch and the screen material being about inch thick. The open area of the screening is about 65% of the total screened area. Sheet metal of about .030 inch thickness may be used for the remainder of the flue assembly. With such a construction, satisfactory combustion and high thermal efficiency, as well as flame stability, are obtained in the presence of substantial winds, e.g. winds of up to at least about 40 miles per hour.

While for best results the inventive construction of inlet chambers and discharge chamber are both employed, less than all of these chambers may be employed while retaining advantage over previously-known flue systems. The delivery conduit system may be other than rectangular and concentric, and the shapes, radii and angles of the apparatus may be varied substantially while retaining all or many of the advantages of the construction.

Accordingly, while the invention has been described in the interest of definiteness with particular reference to a specific embodiment thereof it will be understood that it may be embodied in any of a variety of forms diverse from that specifically described without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. Flue apparatus comprising:

combustion-air inlet chamber means having an inlet orifice for receiving ambient combustion air and an outlet connectable to the combustion-air inlet of a furnace;

flue-gas discharge chamber means having a discharge orifice for discharging flue gas to ambient;

said inlet chamber means and said discharge chamber means being positionable on one side of a wall of an enclosure so that said inlet orifice and said discharge orifice are substantially flush with the external surface of said wall; and

a discharge stack extending upwardly to the underside of said discharge chamber means and having a top opening communicating with the interior of said discharge chamber means between said discharge orifice and the opposite end of said discharge chamber means, said stack having another opening below said top opening connectable to the flue outlet of a furnace and having a lower opening positioned below said other opening and communicating with ambient;

the interior of said discharge chamber means being configured to reverse the flow of air due to wind incident upon said discharge orifice and to divert said flow outward across said top opening.

2. The apparatus of claim 1, in which said combustionair inlet chamber means comprises a chamber having a concave interior surface at its closed end for producing a circulatory flow of air in said chamber in response to wind.

3. The apparatus of claim 2, comprising air deflector means adjacent said inlet orifice and exposed to said wind for deflecting said wind into said inlet chamber means at an angle to enhance said circulatory flow.

4. The apparatus of claim 2, comprising a ventilator chamber above said discharge chamber means and communicating at its lower side with said combustion-air inlet chamber means.

5. In a sealed-combustion system including a sealedcombustion furnace disposed on one side of an enclosure wall and having a combustion-air inlet and a flue-gas outlet, combustiton-air intake means connecting said inlet to the opposite side of said wall to supply the inlet of said furnace with combustiton air from said opposite side of said wall, and flue-gas venting means connecting said furnace outlet to said opposite side of said wall to discharge flue gas from said furnace to said opposite side of said wall, the improvement wherein:

said flue-gas venting means comprises a generally-upright flue stack adjacent said one side of said wall and having a top opening, a lower opening positioned downwardly of said top opening, and an intermediate opening between said top and lower openings communicating with said furnace outlet, said venting means also comprising a discharge chamber disposed above said top opening on said one side of said wall, said chamber communicating with said top opening and having a discharge opening positioned to discharge said flue-gas from said top opening of said stack to said opposite side of said wall, said discharge chamber having an interior surface extending from said top opening away from said wall and configured so that wind arriving at said discharge opening from said opposite side of said wall is circulated inward around the interior of the closed end of said chamber and outward over said top opening to minimize back-pressure at said top opening due to said wind.

6. Apparatus in accordance with claim 5, in which at least a portion of said interior surface is substantially semicylindrical.

7. The apparatus of claim 5, comprising a lip extending upward along the edge of said top opening adjacent said interior surface.

8. Apparatus in accordance with claim 5, in which said combustion-air intake means comprises an air-delivery conduit having an air-receiving end and an air-delivery end for delivering combustiton air to said furnace inlet, in which said combustion-air intake means also comprises an inlet chamber having an air-receiving orifice exposed to ambient air at said opposite side of said wall and having an outlet orifice for transferring combustion air from said opposite side of said wall to said air-delivery conduit, and in which said inlet chamber has a portion extending rearwardly away from said wall beyond said outlet orifice to reduce the effect on combustion-air flow of wind incident on said air-receiving orifice.

9. In a flue system, a discharge chamber for delivering warm exhaust gases from a supply opening to a discharge orifice subject to incident wind, comprising a top surface above, and a bottom surface below, said orifice; one of said surfaces containing an aperture communicating with said supply opening, said chamber also comprising a curved surface extending on the opposite side of said aperture from said orifice and connecting said top and bottom surfaces for guiding wind-induced air flow around said curved surface and outwardly over said aperture.

10. The chamber of claim 9, comprising a lip member extending outward from said one surface along the edge of said aperture adjacent said curved surface, for modifying said outward air flow.

11. The chamber of claim 9, in which said aperture is in said bottom surface.

12. The chamber of claim 11 in which said curved surface is substantially semi-cylindrical and said aperture extends across substantially the entire width of said one surface.

13. In a flue system comprising chamber walls, a first opening in one of said walls exposed to wind and a second opening in said chamber walls, said chamber having an interior concave wall facing said first opening and extending on the opposite side of said second opening from said first opening and responsive to wind entering said first opening to produce a circular flow of air around said concave wall and across said second opening from said opposite side.

14. In a flue system, an inlet chamber for stabilizing the flow of air into an outlet opening from an inlet orifice exposed to wind, comprising chamber walls having an inlet orifice therein and having an outlet opening therein spaced from said inlet orifice, said chamber walls comprising a curved concave interior surface on the opposite side of said outlet opening from said inlet orifice for redirecting wind-induced air currents entering said inlet orifice so that they flow along said curved surface and then outwardly across said outlet opening.

15. In the flue system of claim 14, air deflector means exposed to said winds and extending from and communicating with the interior of said chamber at a position adjacent said inlet orifice, said deflector means being angled to direct wind incident thereon transversely across the interior of said chamber toward the side of said chamber at the opposite end of said concave wall from said outlet opening.

References Cited UNITED STATES PATENTS 3,327,609 6/1967 Sage et a1. 98-62 3,410,193 11/1968 Clark.

CHARLES J. MYHRE, Primary Examiner US. Cl. X.R. 9862; 126--307