Gas-fired Furnace

Abstract

Each heat exchanger cell mounted in the heat tunnel has an elongated flue gas passage of serpentine form. One end of the passage is formed with a burner inlet combustion chamber with means to receive a burner, and the opposite end of the passage communicates with a flue gas discharge opening connected to an induced draft system. The intermediate portion of the flue gas passage extends through a return bend section which is located at the inlet end of the heat tunnel. The sides of the heat cell diverge in a direction from the return bend portion toward the inlet combustion chamber. A blower creates an air flow against the return bend portion and through the tunnel in contact with the sides of the cells. The heat exchanger cells and the sides of the heat tunnel are arranged to provide a vaned-diffuser effect in the heat tunnel.

Description

BACKGROUND OF THE INVENTION

In recent years, attention has been given to the design and construction of gas-fired furnaces of reduced overall dimensions and with sufficient heat output capacity to meet the conventional requirements for domestic heating. While some of such furnaces are smaller than previous units for the same heat output, it is yet most desirable to further reduce the size of the furnaces and to incorporate therein a structural arrangement which will operate with higher heat transfer effectiveness and which may be manufactured and serviced at less cost.

My invention has as an object a gas-fired furnace, particularly suitable for domestic space heating and which embodies a structural arrangement resulting in a substantial reduction of the overall dimensions of the furnace but with an unusually high ratio of heating capacity relative to fuel and power consumption. Due to the unique structural arrangement and configuration involved, the furnace of my invention permits the convenient addition of accessories such as humidifiers, cooling coils, and the like. The design provides high air flow for certain cooling applications, and the combustion system is particularly suited for a multipoise operation.

SUMMARY OF THE INVENTION

One or more heat exchanger cells are mounted in a heat tunnel arranged in a casing. Each heat cell has an elongated flue gas passage of serpentine form extending from an inlet combustion chamber to a discharge opening. The flue gas passage includes a return bend portion positioned near the inlet end of the heat tunnel. The sides of the heat cell diverge from the return bend portion toward the combustion chamber and the exit opening of the heat tunnel.

The side surfaces of the heat exchanger cells are aerodynamically smooth, and the heat cells are disposed in the tunnel in flabelli or fan-like form, providing a vaned-diffuser effect for the efficient movement of air through the heat tunnel in contact with the heat exchanger cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a furnace structure embodying my invention;

FIG. 2 is a front elevational view with parts broken away and parts shown in section;

FIG. 3 is a view taken on a line corresponding to line 3--3 of FIG. 2;

FIG. 4 is a view taken on a line corresponding to line 4--4 of FIG. 2, the gas burners being omitted;

FIG. 5 is a view corresponding to line 5--5 of FIG. 4;

FIG. 6 is an end elevational view of a heat cell as positioned in FIG. 4 looking to the right; and

FIGS. 7-10 are sectional views through the flue gas passage of the heat cell, the views being taken respectively on the lines 7--7 through 10--10, FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The furnace consists of a casing formed of sheet material, such as sheet metal, and having side walls 20,21, an upper front fixed wall 22, and a lower removable front wall 23. The rear wall is indicated at 25 (FIG. 4). The upper portion of the casing contains a heat tunnel having diverging opposed side walls 30,31 and a rear wall 32. The side walls 30,31 are formed along their forward edges with laterally extending flanges 33 abutting the forward casing wall 22 and being affixed thereto as by screws 35 (see FIGS. 3 and 5). The rear wall 32 of the heat tunnel is attached to the rear wall 25 of the casing by a bracket 37 (see FIGS. 3 and 4). The side walls 30,31 of the heat tunnel diverge upwardly (see FIG. 5). The side wall 30 is shown as being located closer to the side wall 20 than is the side wall 31 to the casing side wall 21.

One or more heat exchanger cells 40 are mounted in the heat tunnel. As illustrated in the drawings, there are three heat exchanger cells arranged in the heat tunnel. The heating capacity of the furnace is determined by the number of cells used. Each heat cell 40 is formed with an inlet combustion chamber 41 arranged in registration with an opening 42 (FIG. 4) formed in the upper front wall 22 of the casing. Each heat cell is formed with a radial flange 43 encircling the open end of the combustion chamber. This flange is formed with apertures 45 to receive fasteners 47 extending through apertures formed in the front plate 22 and threading into the apertures 45 in the heat cell flanges. The fasteners 47 may also serve to attach a gas burner 48 to the wall 22 in registration to each combustion chamber 41.

Each heat cell is formed with an elongated flue gas passage of serpentine form extending from the combustion inlet chamber 41 to a discharge opening. Referring to FIG. 4, the combustion chamber 41 is in the form of a linear portion extending inwardly from the inlet opening and merging with a downwardly curved portion 50. The curved portion 50 merges with a return bend portion 51 extending from the figure line 9-9 in the right hand portion, FIG. 5, downwardly around the bight 53, and upwardly to the dashed line 56.

The return bend portion 51 joins with a reversely curved area 57 forming part of an exit portion 59 which communicates with a flue gas discharge opening 60. The discharge opening 60 of the heat exchanger cell is encircled by an outwardly flaring flange 61 abutting against a plate 63 (see FIGS. 3 and 4). The plate 63 inclines downwardly and rearwardly from the front wall 22 and is formed at each side edge with a forwardly bent flange 65. The flanges 65 are attached to the side walls 30,31 of the heat tunnel as by screws 67. The front wall 22 is also formed along each side edge with a forwardly bent flange 70 which is attached to the casing side walls 20,21 as by screws 71.

A floor plate 73 is formed at each end with a downwardly bent flange 75 which is attached to the casing side walls 20,21 as by screws 76. The screws 71,76 in side wall 20 appear in FIG. 1.

The floor plate 73 extends inwardly under the lower edge of the front plate 22, and continues on a slight distance past the lower edge of plate 63. The plates 22,63,73 and tunnel sides 30,31 form a flue gas collector chamber 77 (FIGS. 3 and 4) for reception of flue gases discharged from the heat exchanger cells. The flue gases and products of combustion are moved through the serpentine flue gas passage into the flue gas collector chamber 77 by a combustion suction fan 78 driven by a motor mounted in housing 79. The fan 78 is mounted in a fan housing 80 attached to a plate 81 overlapping the lower part of the front wall 22 and secured thereto as by screws 83. The plates 22,81 are formed with an opening 85 (see FIG. 4) in registration with the intake of fan 78. The flue gases are drawn from the collector box through the passage 85 and are discharged into a vertical drafthood 90 located in an area aligned with the space between the heat tunnel side wall 31 and the casing side wall 21 (see FIGS. 1, 2, and 3).

The casing side wall 21 at its upper edge is bent inwardly to form a flange 91. The inner edge of the major portion of flange 91 is bent upwardly forming a flange 92. The upper end of the tunnel side wall 31 is fixed to the flange 92. The opposite casing side wall 20 is bent inwardly along its upper edge to form flange 94 which is bent upwardly to form a flange 95 to which the upper end of the opposite tunnel wall 30 is affixed (see FIGS. 1, 3, and 5). The rear casing wall 25 is also bent inwardly along its top edge, as at 96. An angle member 97 is fixed to the flange 96 forming a flange 98 to which the rear heat tunnel wall 32 is affixed (FIGS. 3 and 4).

A plate 100 is mounted on the forward portions of the inwardly bent flanges 91,94 on the casing side walls 20,21. The plate 100 is formed with a full length depending flange 101 extending transversely across the top portion of the cabinet (see FIG. 1). The plate 100 is formed with a circular opening in which a circular flange 103 is mounted, and serves for the connection to an exhaust stack (not shown). The major portion of the plate 100 is bent upwardly along its rear edge to form a flange 105 to which the upper end of the front plate 22 is fixed. The flanges 92,95,98, and 105 serve for the convenient attachment of a duct system to the upper end of the heat tunnel.

The side walls 30,31 of the heat tunnel incline downwardly and rearwardly from the inner end of the floor plate 73 (see FIGS. 3 and 4). These inclined edges of the tunnel side walls are flanged outwardly as at 110. The rear wall is inclined downwardly and forwardly as at 111. The lower edge of the inclined portion 111 is formed with a channel 112 for the reception of a flange 113 formed on the wall 114 of a blower housing 115. The side walls of the blower housing 115 are formed, at the discharge of the blower, with similar flanges 117 which abut against the flanges 110. With this arrangement, the blower housing 115 is attached to the lower end of the heat tunnel by the channel formation 112 and by screws 118, fixing the side flanges 117 to the flanges 110 on the tunnel walls 30,31. The blower housing is also supported by angle brackets 119 fixed to the floor plate. An impeller 123 is mounted on the output in the housing 115 and serves to create an air flow upwardly through the heat tunnel and in contact with the outer surfaces of the heat exchanger cells 40.

The gas burners 48 may be of any suitable type which will operate to efficiently supply gaseous hot products of combustion to the inlet combustion chambers 41 of the heat exchanger cells. In FIG. 1, the burners 48 are supplied by a manifold 130 connected to a control mechanism 131 supplied with gas from a conduit extending through the aperture 132 in the side wall 20 of the casing. By operation of the combustion fan 78, the flue gases are drawn downwardly around the bight 53 of the return bend portion 51 of the flue gas passage and thence upwardly and outwardly into the flue gas collector chamber 77. The exhaust gases are then moved upwardly through the drafthood 90 to the stack connected to the flange 103.

The structural arrangement of the heat cell 40, its position in the heat tunnel, the arrangement of the heat tunnel, and the arrangement of the air circulating blower 115 are important features of this invention.

The heat exchanger cell 40 is formed of a pair of complemental mating sections or side members which are formed with confronting concavities which, when the sections are fixedly secured together, form the elongated flue gas passage of serpentine configuration. Each section is formed along its outer edge with a flange 150 and with a similar flange 151 between the inner and outer legs of the flue gas passage (see FIG. 4). The flange 150 has a wider portion 153 intermediate the portions 51,57 of the passage exit portion 59. These flanges 150,151, and 153 are fixedly secured together as by welding or the like.

The flue gas passage is formed with the largest cross-sectional dimension in the area of the combustion chamber 41. As the passage extends from the combustion chamber area 41, it is reduced in cross-sectional area. This reduction will be apparent comparing FIGS. 6,7, and 8. The curved area continues to reduce in cross-sectional area to the return bend portion 51. The beginning of this section is indicated in FIG. 9 of the drawings. This area in the return bend section is uniform from the line 9--9 to at least the dashed line 56 in FIG. 4. The cross-sectional area of the flue passage increases through the exit portion 59 (see FIG. 10).

It will be apparent the elongated serpentine passage of the heat exchanger cell is free of all impedance, such as baffles and the like, to the flow of flue gases through the flue gas passage.

It will be further noted that the return bend portion 51 of the flue gas passage is of reduced width and thickness. This results in creating high velocities in the flue gases with corresponding high flue side heat transfer coefficients. This feature, plus the elongated serpentine passage, results in the heat cell having an unusually small height and width dimension and simultaneously having an unusually high heat load capacity. As will be apparent, this results in a very substantial reduction in the size of the furnace casing in ratio to the heat output of the furnace.

A further feature of the heat cell construction resides in the fact that both the exterior surface of the cell and the side walls of the flue gas passage are free from abrupt discontinuancies. This is not only of importance for the free flow of the flue gases through the flue gas passage, but it is also particularly beneficial in the flow of air through the heat tunnel. Also, the absence of abrupt discontinuancies in the side walls of the heat exchanger cells is of importance in avoiding thermal fatigue of the metal due to possible stress concentration. It should be observed that the most narrow portion or section of the heat cell is positioned at the bottom of the heat tunnel; that is, near the inlet thereof.

Air discharged from the blower 115 is impinged directly upon the return portions of the heat cells; and due to the fact that the sides of the cells are aerodynamically smooth and diverge upwardly, the air flow is moved into efficient contact with the side surfaces of the cells. The flabelliform or fan-like arrangement of the heat cells, in conjunction with the diverging side walls of the heat tunnel, is particularly inducive to the efficient movement of air upwardly through the heat tunnel. With this arrangement, the blower is effective to move the maximum volume of air with minimum consumption of power. This is not only of importance when the unit is operated as a furnace. The unrestricted and even distribution of the air flow upwardly through the tunnel is particularly advantageous when a refrigerant coil is mounted at the upper end of the tunnel for air conditioning during the summer period. It permits full realization of cooling coil performance.

It will be apparent that the particularly efficient heat cells are very economically produced by being stamped and formed from sheet metal, the assembly of the cell only requiring the affixing of the flanges 150,151, and 153 on the mating sections.

While I have illustrated and described a highly practical embodiment of my invention, it is to be understood changes may be made in certain areas of the structural arrangement without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

I claim:

1. A space heating gas-fired furnace formed with a heat tunnel having an inlet opening at one end and an outlet opening at the opposite end, said tunnel being formed with a pair of opposed side walls, a heat exchanger cell mounted in said tunnel and having side walls disposed in spaced relation to said side walls of said heat tunnel, said heat exchanger cell extending in a direction from the inlet opening of said heat tunnel toward the outlet thereof and being formed with a combustion inlet chamber disposed in proximity to said tunnel outlet and a flue gas discharge opening, a flue gas passage extending between said side walls of said cell from said combustion inlet chamber to said discharge opening, said cell side walls diverging in a direction from said heat tunnel inlet opening toward said outlet opening, blower means creating air flow through said tunnel in a direction from said tunnel inlet opening toward said tunnel outlet opening in contact with the exterior surfaces of said heat exchanger cell, and gas burner means arranged in juxtaposition to said combustion inlet chamber for supplying hot products of combustion thereto.

2. A space heating gas-fired furnace as set forth in claim 1 wherein said passage includes a return bend portion positioned at said tunnel inlet opening, said side walls of said cell diverging in a direction from said return bend portion toward said outlet opening of said tunnel.

3. A space heating gas-fired furnace as set forth in claim 1 wherein said opposed side walls of said heat tunnel diverge in a direction from the inlet opening of said tunnel toward the outlet opening thereof.

4. A space heating gas-fired furnace as set forth in claim 1 and including a plurality of said heat exchanger cells mounted in spaced apart side-by-side relation in flabelliform in said heat tunnel, said cells extending from said inlet opening of said tunnel toward the outlet opening thereof, the cells at one side of the lengthwise axis of said tunnel diverging from the cells at the opposite sides of said axis, in a direction toward said tunnel outlet opening, said opposed side walls of said tunnel diverging in a direction from the inlet opening of said tunnel toward the outlet opening thereof, said cells serving as diffuser vanes and in conjunction with the diverging sides of said tunnel enhancing the uniform flow distribution of air through said heat tunnel.

5. A space heating gas-fired furnace comprising a casing formed with a heat tunnel, a heat exchanger cell mounted in said tunnel and extending lengthwise thereof, said cell being formed with a burner inlet opening and a flue gas discharge opening, said openings being connected by an unimpeded flue gas passage of general serpentine form for the free flow of flue gases from said burner inlet opening to said discharge opening, said flue gas passage including a return bend portion intermediate said burner inlet opening and said flue gas discharge opening, said flue gas passage having a linear inlet portion extending inwardly from said inlet opening to a curved portion, said curved portion communicating with said return bend portion, said return portion terminating in a reversely curved exit portion, said exit portion communicating with said flue gas discharge opening, a power-operated blower mounted in said casing and having an outlet positioned contiguous to said return bend portion of said cell for the impingement of air thereon, said blower being operable to create an air flow through said heat tunnel in contact with the side surfaces of said cell, and gas burner means arranged in operating relation to said burner inlet opening for supplying hot products of combustion thereto.

6. A space heating gas-fired furnace as set forth in claim 5 wherein said flue gas passage diminishes in cross-sectional area from said inlet opening to said return bend portion, and increases in cross-sectional area from the said return bend portion to said discharge opening.

7. A space heating gas-fired furnace as set forth in claim 5 wherein the side walls of said heat exchanger cell are free from abrupt discontinuances.