US3358672A - Gas-fired furnace - Google Patents

Description

Dec. 19, 1967 w` R. DIRK ET AL GAS-FIRED FURNACE Filed March l5, 1966 3 Sheets-Sheet l Inenzonsf' Dec. 19, 1967 w` R. DIRK ET AL Y 3,358,672

GAS-FIRED FURNACE Filed March 15, 1966 3 Sheets-Sheet a Dec. 19, 1967 w.A R. DIRK ET AL GAS -FIRED FURNACE Filed March 15, 1966 3 Sheets-Sheet 3 Y z'r/f Clifford Pezenson United States Patent O 3,358,672 GAS-FIRED FURNACE William R. Dirk and Clifford D. Peterson, Marshalltown, Iowa, assignors to Lennox Industries Inc., a corporation of Iowa Filed Mar. 15, 1966, Ser. No. 534,499 2 Claims. (Cl. 126-110) ABSTRACT F THE DISCLOSURE A heat exchanger made from sheet metal components including an enlarged centrally disposed burner tube, a rear breeching secured to the burner tube, a plurality of tubes disposed about the burner tube and connected at the rear to the rear breeching and at the front to the front breeching. The front breeching has an enlarged opening through which the burner tube extends. The front breeching is connected to an upright vestibule panel for supporting the heat exchanger horizontally in a furnace cabinet so that air to be heated can pass over all effective heat transfer surface. The rear breeching is not connected to the furnace cabinet.

This invention relates to gas-tired furnaces and, more particularly, to improved heat exchanger construction and burner means for use in such furnaces. Further, this invention relates to an improved burner arrangement that is adapted to cooperate with a novel tube-type heat exchanger that provides higher heating capacity with less heat exchanger surface and is manufactured readily and relatively inexpensively by hydrogen brazing.

Heretofore, a common heat exchanger-burner construction for a gas furnace has comprised a heat exchanger formed by a number of clamshell sections each defined by symmetrical sheet metal members joined to one another by planar peripheral flanges. The sheet metal members are spaced apart to dene a lower `burner chamber, an intermediate chamber and yan upper flue gas chamber. Disposed within each burner chamber is an elongated ribbon-type or the like gas burner.

The present invention is concerned with a novel tubetype heat exchanger design which utilizes available heat transfer surface more effectively than conventional clamshell-type heat exchangers. Furthermore, the process of combustion is completed in a new burner arrangement that utilizes one-hundred-percent secondary air and is operatively associated with the novel heat exchanger so as to provide an assembly -that is non-position sensitive and can be operated in horizontal, upright or d ownow applications. Other advantages and features of the present invention will become more apparent hereinafter.

FIG. 1 is a perspective View of an up-flow type gas furnace embodying the present invention;

G. 2 is a partial cross-sectional View of the gas furnace of FIG. l showing the novel heat exchanger construction and the unique burner means of the present invention;

FIG. 3 is a cross-sectional view of thenew heat exchanger construction taken generally along line 3-3 of FIG. 2;

FIG. 4 is -an elevation view of the heat exchanger construction;

FIG. 5 is an end view of the heat exchanger illustrating the vestibule panel thereof;

FIG. 6 is a cross-sectional View of the burner means taken generally along line 66 of FIG. 2;

FIG. 7 is a cross-sectional view of the burner means taken generally along line 7-7 of FIG. 6;

FIG. 8 is a cross-sectional view of the burner means taken generally along line 8 8 of FIG. 6; and

FIG. 9 is a cross-sectional view of the burner means illustrating the gas spreader in plan.

Referring now to FIG. 1, there is shown a gas furnace 10 embodying the heat exchanger and the burner construction of the present invention. The gas furnace 10 comprises a box-like housing or cabinet 12 having an open front closed by a pair of removable access panels 13 and 14. In the lower portion of the cabinet is an inlet (not shown) communicating with a return air duct from the area to be treated. The outlet 16 in. cabinet 12 communicates with a duct for forwarding treated air to the area to be conditioned.

Within the furnace 10 is a blower for moving airY through the furnace over the heat exchanger thereon. The rburner means within the furnace is connected to a conduit 18 which is in turn connected to a source of gaseous fuel, for example, natural gas. Suitable electrical switch means 20 are provided for selectively controlling the operation of the blower in the furnace.

Referring to FIG. 2, it is noted that blower 22 is provided to circulate air through cabinet 12 4'and over the novel tube-type heat exchanger 24. The blower 22 comprises a centrifugal fan disposed within a scroll affixed to the cabinet 12. In the up-flow furnace illustrated,"air to be treated enters cabinet 12 through a suitable opening in the side of the cabinet in the lower portion thereof, passes through the blower and over the heat exchanger in heat transfer relationship with the exterior surfaces thereof, and exits from cabinet 12 through opening 16 in the top thereof. The up-liow type furnace has been shown to illustrate one form of furnace utilizing the present invention. As will be pointed out hereinafter, the heat exchanger 24 and burner means 26 are constructed and arranged so that they are non-position sensitive and can function equally well in horizontal flow and down-flow furnace applications. Basically, in a horizontal flow application, -the longitudinal axis yof the furnace cabinet extends horizontally. For example, the cabinet is rotated clockwise from the position shown in FIG. 1. In a down-flow application, the cabinet is rotated from FIG. 1.

The heat exchanger 24 (FIGS. 2, 3 and 4) comprises a plurality of elongated tubes 28 disposed about an enlarged central tube or cylinder 29, with the tubes 28 being aixed at one end to front breeching 30 and at the other end to rear breeching 32. The central tube 29 is joined to rear breeching 32 and the vestibule panel 34. rear breeching 32 comprises a pair of concave saucerlike members 36 and 37 having peripheral anges 38 and 39 joined to one another to deiine a chamber 40 there- Within which communicates with the interior of burner tube 29. The front section 37 of breeching 32 has a plurality of openings therein for receiving an end of eac-h tube 28 and an enlarged central opening for receiving an end of cylinder 29.

charge through duct 52 to communicate with the flue 3 conduit for discharging the flue gases to the atmosphere.

Preferably, the heat exchanger 24 is comprised of sheet metal members that are joined together by hydrogen brazing techniques. Ho'wever, if desired, the rear section 36 of breeching 32. may be detachably secured to the front section 37, as for example, by nuts and bolts so as to provide for internal cleaning of the tubes.

The vestibule panel 34 (FIGS. 2, 4 and 5) includes a generally upright planar portion 60 having a central circular opening 62 therein for receiving the front end of cylinder 29, a generally square opening 43 communicating with flue gas chamber 46, and access opening 64. A safety control may be ymounted on panel 34 and extend into chamber 46 through opening 64. A flange 66 is provided lon the bottom of panel 34 to facilitate connection of the panel to cross panel 67 in cabinet 12. The top of the vestibule panel 34 includes a portion 68 offset at right angles to the upright planar portion 60, the portion 68 having a generally U-shaped end portion 69. The lportion 68 of the panel 34 is adapted to cooperate with the top 7G of the cabinet 12 and the flange 66 cooperates with the transverse panel 67 to secure the panel 34 in place within the cabinet.

Secured to the vestibule panel 34 and extending into the tube 29 of the heat exchanger 24 is the burner means 26 of the present invention. The burner means 26 (FGS. 2', 6, 7 and 8) comprises a housing 72 to which is secured a combustion air fan or blower means 74. The fan or blower means 74 includes a motor 75 affixed to a centrifugal blower disposed within housing 73 for drawing air into the housing 73 through a suitable opening in the side thereof from the chamber 76 defined between the front of the vestibule panel 34, the cross panel 67, the rear of the removable access cover 14 and the up wardly inclined wall 77 of diverter Si. The centrifugal blower or fan discharges the air into the passage 7S within the housing 72. Divider or air splitter 79 disposed within the housing 72 separates the air into two streams for facilitating more uniform entry of the air into the chamber 92' disposed between the perforated conical funnel member 80 and the housing 72', and` thereby providing more even air distribution over the burner head or member 80.

Gaseous fuel is introduced into the apex end of the conical member 80 through a conduit or pipe nipple 82 which is connected to conduit 18 (FIG. l) that communicates with a suitable source of gas, as for example, natural gas commonly used for residential heating purposes. A metering orifice (not shown) is provided in the manifold assembly upstream from nipple 82. Disposed in the conicall member Si) and secured thereto closely adjacent to the discharge end ofthe conduit 32 is a gas spreader 84 for diffusing the gas discharging into the conical member to effect a better ignition of the gas. The gas spreader best seen in FIG. 9 is in the form of a circular disc which has edge perforations or recesses 83 and is suitably affixed' to the member 80. The gas issuing from the end of nipple 82 passes through the openings defined between the recesses in the gas spreader and the wallof the conical member Si) and tends to move parallel to the wall. This has been desirable to promote combustion of the gas.

The gas is ignited in a conventional manner by means of a spark plug electrode member 86.` The spark plug S6 is suitably secured to the conical member 80 adjacent the outlet from the conduit 82 by means including bracket 87 on housing 72. A fla-me protector sensor is provided and is secured in an electrical circuit with the spark plug electrode S6 in a conventional manner. Disposed over the surface of the conical member 80 is a screen member 90 which is adapted to diffuse the air entering the conical member and to reduce the noise level of the moving air stream. One type of screen member that has been found satisfactory has been made from stainless steel having 20 wires per inch.

It is to be observed that air enters the housing 72 only through the passage 78 for discharge into the chamber 92 defined between the exterior of the perforated conical member and the interior of the housing 72. As best seen in FIG. 6, the openings 93 are disposed about the entire surface of the conical member 80. Thus, onehundred-percent secondary air is introducedl in a positive fashion into the chamber 92 by means. of the combustion air blower or fan means 74. Gas from the conduit 82 is measured into the center of the funnel through the opening at the exit or discharge end of the conduit 82 and combustion takes place just off the burner face with burnout or combustion being completed within 8 to l0 inches from the face of the burner. The annular retension ring 96 secured to the base of the conical member 80 helps to direct the flame into the central part of tube 29. Advantages of this construction are that much space is conserved, fewer parts are employed and combustion is not critical to the air ratio mixture since the invention utilizes one-hundred-percent secondary air, that is, all the combustion air is introduced into the burner head through openings 93 for mixture with the fuel discharging from nipple S2.

Suitable access opening means 98 (FIG. 8) may be provided for housing 72. The access opening means may comprise an opening in housing 72 adapted to be closed during operation of the burner by a cover pivotally carried on the housing.

As aforenoted, the electrical ignition system may be of conventional design and may include a solid state flame ignitor, a flame sensor, limit controls and the other electrical devices commonly utilized in such system.

The unique cooperation between the burner means and the heat exchanger provides a furnace having a higher efficiency than conventional clamshell-type furnaces. The efficiency of a gas furnace is ordinarily determined by the ue temperature, carbon dioxide gas method. By means of the present invention, it is possible to maintain both a high carbon dioxide output and a low ue gas temperature which, in` effect, determines the high rate of efficiency for the present invention. The resultant combustion process in the present invention is better than that of conventional atmospheric primary, secondary air gas furnaces.

Anotheradvantageof the present heat exchanger construction is that it may be used advantageously in the event that air conditioning evaporator coils are provided with the furnace. It is known that in air conditioning applications, more air must pass through the system to accomplish the desired conditioning of the room to be treated than isrequired for heating applications. Normally, with clamshell-type heat exchangers, baffles and other air guide means are provided to keep the heat exchanger steel Within the allowable temperature conditions. The introduction of such baffles adds a restriction to the flow of air. Provision of baffling which is proper for satisfactory furnace operation, may limit undesirably the air delivery capacity of the furnace blower for air conditioning purposes.

The new tubular-type heat exchanger of the present invention is aerodynamically proper for good air wiping on the heating application lso as to permit maximum heat transfer between the hot lgas in the tubes 28 and the air to be conditioned passing over the tubes, andl is not as restrictive for higher air volumes, such as are required for air conditioning, as conventional furnaces. Thus, the present furnace design does not require 'baies to provide the proper air for heating and by increasing the blower output, a very satisfactory air conditioning air delivery can now be obtained. An important factor which dictates the size of the cabinet means of a furnace unit is the size of the blower for moving air through the cabinet and thus a relatively smaller Iblower can be effectively utilized by .the present invention to obtain desired air conditioning output.

Whereas conventional clamshell-type heat exchangers are formed from stamped sheet metal sections welded together along the peripheral edges, the present heat exchanger design lends itself to a very inexpensive joining process known as hydrogen furnace brazing. The components of the present heat exchanger 24 are substantially all tubular and can be pressed together to become selfjigging and self-supporting while going through the hydrogen brazing process. There is a material reduction in welding time and the cost of Welding of the components to one another is materially reduced by the present invention.

The heat exchanger and burner means are compact and the over-all size of a furnace cabinet can be substantially reduced by utilization of the present invention. For example, one type of clamshell-type heat exchanger for producing 80,000 B.t.u.s per hour input is housed in a cabinet 16 inches wide by Z6 inches deep by 48 inches tall. A comparable furnace embodying the principles of this invention for producing 80,000 B.t.u.s per hour input may have a total cabinet size inches wide by 26 inches deep by 40 inches tall. With larger capacity units, even greater reduction in size of the furnace cabinet is possible.

Since the 4burner utilizes one-hundred-percent secondary air supplied by means of the blower 74, the device is not sensitive to position and can be used in up-llow, down-flow and horizontal-flow furnace applications.

It is to be noted that utilization of the present invention permits obtaining very hi-gh capacities of heat transfer as compared with conventional clamshell heat exchangers. Heat exchangers embodying the present design have been tested up to 600,000 B.t.u.s per hour of gas input with satisfactory results. Unexpectedly, it has been found that these results have been obtained on the basis of utilization of 17 or 18 square inches per 1000 B.t.u.s per hour of input of primary and secondary heat exchanger surface as compared to 37 to 38 square inches per 1000 B.t.u.s per hour of input on conventional clamshell furnaces.

In certain applications utilizing the burner and heat exchanger of this invention, it is possible because of the positive pressurization of the burner to seal olf the flue duct 52. from the furnace room and to use a smaller diameter flue duct 52. There is provided a power vent for effectively removing flue ygas from the furnace.

For outdoor use, the diverter is unnecessary and flue gas outlet may be connected directly to the atmosphere.

The novel heat exchanger cooperates with the burner means to provide a gas-fired furnace that operates with a higher eciency than conventional furnaces. 'The combustion process in the new and unique burner utilizes one-hundred-percent secondary air that is supplied with a small centrifugal combustion air blower. The heat exchanger construction is relatively simple in construction and inexpensive to fabricate. During use, the front breeching is secured to the vestibule panel only at the flue outlet and to the rear breeching only by tubes 28. The main burner tube or central tube 29 is secured at the rear to the rear breeching but is not rigidly aflixed to the burner means 26. Thus, the heat exchanger is free to expand and contract without any ticking noises or expansion sounds.

While we have described a presently preferred embodiment of t-he invention, it will be understood that the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

We claim:

1. `In a gas-tired furnace comprising cabinet means having an air inlet and an air outlet and blower means for moving air through the cabinet means, an upright Vestibule panel disposed in the cabinet means, the vestibule panel having a flue opening therethrough and a burner opening for receiving burner means, a heat exchanger disposed in the air flow path through said cabinet means, burner means associated with said heat exchanger for supplying heated gas thereto and llue means associated with said heat exchanger for receiving heated gas and passing same from said cabinet means, the improvement comprising said heat exchanger being constructed from a burner tube of relatively large cross-sectional area and a plurality of smaller tubes of relatively small crosssectional area, the smaller tubes being secured at their ends to front and rear breechings, the front breeching having a flue outlet, the front breeching being secured to the vestibule panel with the liuc outlet in the breeching being aligned with the flue opening in the vestibule panel, the axes of said smaller tubes being disposed generally parallel to one another and to the axis of the burner tube, said burner tube being centrally oriented and said smaller tubes lbeing disposed about said burner tube, said burner tube being connected to said rear breeching and extending through a central opening in said front breeching and being adapted to receive heated gas from said burner means, the gas passing through the burner tube to the rear breeching and back to the front breeching which communicates with the lue means for discharging gas from the cabinet means, with air passing over the heat exchanger being in heat exchange relationship with the burner tube, the smaller tubes, and the breechings, the axes of the burner tube and the smaller tubes being generally at right angles to the plane of the vestibule panel, said rear breeching being connected to said front breeching only by said smaller tubes and bein-g free to expand and contract longitudinally of the smaller tubes.

2. A gas furnace as in claim i, said rear breeching being made from a pair of saucer-like concave members peripherally joined to one another to dene a rear breeching chamber for receiving burned gas from the burner tube; said rear breeching, said front breeching, said burner tube and said first tubes being made from sheet metal.

References Cited UNITED STATES PATENTS 1,825,735 10/1931 Junkers.

2,263,098 11/1941 Mueller 126-110 3,053,246 9/ 1962 =Kosarn et al. 126-110 3,111,939 11/1963 Peoples 126-104 3,187,799 6/1965 Nesbit 158-109 FOREIGN PATENTS 1,177,306 9/ 1964 Germany.

JAMES V. WESTHAVER, Primary Examiner,

Claims (1)

1. IN A GAS-FIRED FURNACE COMPRISING CABINET MEANS HAVING AN AIR INLET AND AN AIR OUTLET AND BLOWER MEANS FOR MOVING AIR THROUGH THE CABINET MEANS, AND UPRIGHT VESTIBULE PANEL DISPOSED IN THE CABINET MEANS, THE VESTIBULE PANEL HAVING A FLUE OPENING THERETRHOUGH AND A BURNER OPENING FOR RECEIVING BURNER MEANS, A HEAT EXCHANGER DISPOSED IN THE AIR FLOW PATH THROUGH SAID CABINET MEANS, BURNER MEANS ASSOCIATED WITH SAID HEAT EXCHANGER FOR SUPPLYING HEATED GAS THERETO AND FLUE MEANS ASSOCIATED WITH SAID HEAT EXCHANGER FOR RECEIVING HEATED GAS AND PASSING SAME FROM SAID CABINET MEANS, THE IMPROVEMENT COMPRISING SAID HEAT EXCHANGER BEING CONSTRUCTED FROM A BURNER TUBE OF RELATIVELY LARGE CROSS-SECTIONAL AREA AND A PLURALITY OF SMALLER TUBES OF RELATIVELY SMALL CROSSSECTIONAL AREA, THE SMALLER TUBES BEING SECURED AT THEIR ENDS TO FRONT AND REAR BREECHINGS, THE FRONT BREECHING HAVING A FLUE OUTLET, THE FRONT BREECHING BEING SECURED TO THE VESTIBULE PANEL WITH THE FLUE OUTLET IN THE BREECHING BEING ALIGNED WITH THE FLUE OPENING IN THE VESTIBULE PANEL, THE AXES OF SAID SMALLER TUBES BEING DISPOSED GENERALLY PARALLEL TO ONE ANOTHER AND TO THE AXIS OF THE BURNER TUBE, SAID BURNER TUBE BEING CENTRALLY ORIENTED AND SAID SMALLER TUBES BEING DISPOSED ABOUT SAID BURNER TUBE, SAID BURNER TUBE BEING CONNECTED TO SAID REAR BREECHING AND EXTENDING THROUGH A CENTRAL OPENING IN SAID FRONT BREECHING AND BEING ADAPTED TO RECEIVE HEATED GAS FROM SAID BURNER MEANS, THE GAS PASSING THROUGH THE BURNER TUBE TO THE REAR BREECHING AND BACK TO THE FRONT BREECHING WHICH COMMUNICATES WITH THE FLUE MEANS FOR DISCHARGING GAS FROM THE CABINET MEANS, WITH AIR PASSING OVER THE HEAT EXCHANGER BEING IN HEAT EXCHANGE RELATIONSHIP WITH THE BURNER TUBE, THE SMALLER TUBES, AND THE BREECHINGS, THE AXES OF THE BURNER TUBE AND THE SMALLER TUBES BEING GENERALLY AT RIGHT ANGLES TO THE PLANE OF THE VESTIBULE PANEL, SAID REAR BREECHING BEING CONNECTED TO SAID FRONT BREECHING ONLY BY SAID SMALLER TUBES AND BEING FREE TO EXPAND AND CONTRACT LONGITUDINALLY OF THE SMALLER TUBES.

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