US2302235A - Furnace - Google Patents

Description

o air.

Pefenied Nev. 17, 1942 UNITED sTATEsrATENT oFFICi:

Russell Martin, Wichita, Kans., assignor to The Coleman Lamp and Stove Company, Wichita, Kans., a corporation of Kansas Appxieatien April 3, 1941, serial No. 386,595

4 claims. (Cl. 12s-.116)

This invention relates to furnaces, particularly the type known as floor furnaces wherein air is circulated downwardlywithin the furnace and then upwardly around the heater unit, the circulation being maintained responsive to difference in temperature of the up andA lclown streams of inner jacket which divides the streams of air and this jacket is constructed as an insulating member with a liner to reflect radiated heat therefrom y and p'revent its absorption by the inner jacket.

It is the practice to space this liner-slightly from the jacket to prevent heat from being transmitted to the downward moving column of cool air which ows from the oor-of vthe room above. Present structures, however, fail to adequatelyperform this purpose to secure the best operation. Furnaces of .this type must be small in size to be installed in limited spaces and the inner parts, therefore, must be compactly arranged, thus making the air passages relatively, narrow. This somewhat restricted space for the moving columns of air tends to slow up air circulation, causing that portionV of the upwardv moving air column which contacts the combustion chamber to be heated to such an excessive temperature that the total quantity of the air being discharged from the furna-ce'is often expanded to more than one and one-half times its volume at room temperature. This, in turn, tends to restrict the actual quantity of the air moved through the Usually such a furnace is provided with anl tion. Therefore, an object of this invention is to provide an improved structure for this type of furnace which will greatly increase the air flow therethrough, without increasing the over-all size of the furnace andits floor register 'and to ob-l tain this result by natural draft without the aid of `mechanical means, such as electricians and blowers, which add to the cost of structure and to costof operation.

A further object of the invention is to provide a better. distribution oi? the heat over the entire discharge area Aof the furnaceso as to better employ the entire capacity of the furnace to dis-` charge the heat produced .therein and 'to prevent n hot spots in any portion of the discharge area.

stantially uniform temperature, and to be safe furnace, which in turn causes overheating within u the furnace. Furthermore, the excessively high temperature of the central portion of the air 'column 'tends to overheat the central portion of the floor register, thus introducing an element of danger, both to persons and to materials which may come in contact with same. The present structures in use depend on air insulation and reflecting surfaces to keep the downward moving column of air between the jackets from heating, but this reflected heat causes the 'combustion chamber itself to become hotter and to have a.

lowered thermal emciency. The upward moving columns of air must be heated almost entirely by contact with the combustion chamber itself, with the result that only the central portion of the column of air being delivered from the furnace is moving rapidly while the major portion of the air column, removed from the center, is so low in temperature that its movement is sluggish, the net result being that the total quantity of air being discharged is not'suicient to effect a desirable low temperature operation. Large air circulation the invention, as hereinafter pointed out, I have is, however, essential for efficient furnace oper-a- 55 that temperature must not greatly exceed room temperatures. In practice this control is placed in ythe cool downward flowing air between the outer and inner jackets. This space must, therefore, have a temperature during operation not greatly in excess of'room' temperatures. A further object of this invention is to 'provide' a structure which maintains the. temperature of this section of the furnace nearer that of the room temperature, thus insuring a more uniform operation of the fuel metering valve, object is to reduce production costs.

In accomplishing these and other objects of A st-ill further provided improved details of structure, the preferred form of which is illustrated in the accompanying drawing, wherein:

Fig. 1 is a horizontal section through a iioor furnaceembodying the features ofthe present invention. f k p o Fig. 2 is a vertical section through the furnace.

Fig. 3 is a fragmentary perspective view of the inner jacket and .heat transformer of the floor furnace. e

Referring more in detail to the drawing:

The floor furnace includesan .outer'casing i comprising side walls 2--3 connected with ,front f and rear walls 4--5 and a bottom 6. The marginal portion of the bottom 6 is preferably curved inwardly and downwardly as at 1 to connect with an upwardly crowned central portion 8 by inclined portions 9. The upper edges of the side walls are provided with laterally extending flanges I adapted to seat on the edges of a floor opening which receives the furnace. The outer casing is covered by a floor grill II usually formed of metal and having support at the marginal edges upon the flanges I0. Suitably supported within the casing or outer jacket is an inner jacket I2 having side walls I3-I4 and front and back walls I5-I6 which are spaced inwardly from the corresponding walls of the casing or outer jacket to form down-draft passageways I1. The lower edges I8 of the jacket I2 are spaced from the inclined bottom portions 9 of the casing to provide passages I9 thereunder through which downwardly moving streams of yair are diverted upwardly into contact with a heating unit 20. In order to facilitate downward movement of air through the margins of the floor grill, the upper portions of the inner jacket are inclined inwardly, as at 2l, to provide widened throats 22 for the passageways Il and to form a nozzle-like discharge 23 for the upwardly moving streams of heated air. as later described. In the illustrated instance, the inner jacket is shown as 4supported on a frame 24 carried on brackets 25 fixed to the walls of the casing, which frame also carries the heating unit 2U.

The heating unit includes an elongated combustion chamber 26 having front and rear walls 21 and 2B connected with substantially semicylindrical end walls 29 and 30 which are spaced from the corresponding walls of the inner jacket to provide passageways 3i for the air. The top of the combustion chamber is closed by a cover 32, having openings 33 at the ends thereof closed by lids 34 through which access is had to the interior of the chamber. The. bottom of the combustion chamber 26is closed by a horizontal partition 35, inset within the walls of the chamber and spaced from a lower end 36 to form aburner chamber 31 therebetween. The end 36, the partition and the cover 32 are provided with openings 38 in the central Aportions thereofv through which an up-draft tube 39 extends and 'which is adapted to increase the heat transmitting surfaces of the combustion chamber. Suspended in openings 40 formed in the partition 35, are burners 4I, which, in the illustrated instance, are designed for a liquid fuel which is admitted through ducts 42 connected with a constant level control and safety valve 43, which in turn is connected with a fuel supply line 44, under control of a stop valve 45. The regulating valves 46 controlling the respective fuel ducts 42 to the burners are incorporated in the valve unit 43 and are actuated by rods 41. v The rear wall of the combustion' chamber has a flue outlet opening 43 connected with a draft control. regulator 49, which in turn is adapted to be connected with a flue duct (not shown) as in conventional pracf tice.

When the furnace is in operation, the hot gasesresulting from combustion of the fuel circulate over the inner surfaces of the combustion chamber to heat the walls thereof. The radiated heat from the products of combustion also heats the walls. Some of the heat'is' carried away from the walls of the heater unit by the upwardly movim stream of air. The heater radiates aiarse ing stream of air and unless some means is provided, the radiated heat isabsorbed by the inner jacket and is conducted to the downwardly moving stream of air so that the temperature thereof approaches the temperature of the upwardly moving stream of air. To prevent this heating effect on the downwardly moving stream of air, the inner jacket, as heretofore constructed, is provided with a liner formed of heat reflecting material to reflect the radiant heat away from the inner jacket. Theliner is also spaced slightly from the inner face of the jacket to provide a limited amount of air insulation. As above pointed out, such insulators are ineffective, with the result that the downwardly moving stream of air is heated sufficiently to substantially retard circulation and'overheat the fuel metering valve.

As above stated. it is an object of the present the radiant heat by transforming the radiant heat into 'convectional heat.

In order to carry out the objects of the present invention, I provide the furnace with a heat transformer 5I which encloses the heating unit and divides the up-draft passageway 3l into an inner primary passageway 52 and an outer secondary passageway 53.

The transformer 5I includes front and rear walls 54-55 and side walls 53-51 corresponding to the adjacent walls ofthe inner jacket, previously described. The lower edge 53 of the heat transformer walls is spaced slightly above the edges I8 of the outer jacket to avoid obstructing upward movement of the stream of air through the passageway I9 and better assure division of the air into the primary and secondary streams as shown by the arrows in Fig. 2. The upper ends of the transformer walls are inclined inwardly as at 59 in conformity with the inclined portions 2 I of the jacket I2 and terminate below the upper edge thereof as shown in Fig. l. The transformer walls are thus located in the path of the heat radiated from the heating unit and are formed of a material having high heat absorbing properties to labsorb the radiated heat and prevent its absorption by the inner jacket. In the present instance, the jacket I2 is preferably formed of a heat reflecting material having shiny surfaces Il (Fig. 3) to'reilect any heat that is reradiated from the transformer walls. The transformer is preferably of a metal having a high heat absorbing inner surface, as indicated at 6I. These walls therefore effectively absorb the radiated heat from the combustion chamber.

Attention is also directed to the fact that the walls of the heat transformer are spaced a sumcient distance from the corresponding walls of the inner jacket to provide ample flow capacity therebetween and assure sunicient movement of air to quickly carry away the heat from the walls of the transformer.

As compared to furnaces heretofore constructed, it is now apparent that I have adopted a principle that is new in floor furnacev structure. Instead of using a limited air insulation together witha reflector liner to prevent the radiated heat from the combustion chamber heating the inner Jacket, I have substituted therefor a for I call a heat transformer. By doing this, the following has been accomplished.

Less heat is imparted to the air in the downstream passageway; more of the radiated heat from the heater unit vis absorbed by the heat transformer than was absorbed by the heat refleeting liners; less heat is transmitted from the heat transformer to the inner jacket than was transmitted from the liners to the inner jacket because I have provided ample passageway, for air to circulate freely between the heat transformer and inner jacket so that the heat is carried away by convection; by providing ample circulation between the transformer and inner jacket, the inner jacket is kept cooler and irn-` of it, radiated heat is absorbed from the heater f unit by the transformer and in turn is imparted to the air flowing in contact with it, transforming the radiated heat to convectional heat which passes out through the top of the furnace. In

the conventional furnace the radiated heat is reflected back to the heater unit, maintaining a higher temperature of the walls which, in turn, do not absorb the heat from the products of combustion so readily, causing a higher stack temperature and therefore a lower thermal efliciency than is attained with a furnace having a heat transformer. The furnace discharges air at a more uniform temperature over the hot air discharge section, operates at a lower temperature, and circulates more air. This is because the heat is absorbed by the transformer which in turn heats the air which comes in contact with it, providing a more uniform temperature of the air through the upstream air circulating passageways and hence more uniform temperature of the air passing through the hot air discharge section of the grill. The air in the upstream, coming in contact with more hot surfaces, is heated more rapidly and by being heated more uniformly throughout the upstream passageways, more circulation is obtained. All of this in combination with the more rapidly moving cooler air in the downstream passageway pror casing having interconnected front, rear and side walls connected by a bottom, a jacket having interconnected front, rear and sidewalls spaced inwardly from the corresponding side walls of the casing to form downflow passageways with the lower edges of said walls spaced from said bottom,` a heat absorbing jacket having walls conforming to the rst named jacket and spaced inwardly therefrom to provide secondary air passageways between the jacket walls, said passageways being connected with the downiiow passages by reason of said spaced lower edges, a heating unit supported within said heat absorbing jacket, and a constant level fuel control valve located within said casing near the connection of one of the downow passages with a secondary passageway for controlling fuel vsupply to, the burner.

2. A liquid fuel burning furnace including a casing having interconnected front, rear and side walls connectedA by a bottom, a heat reflecting jacket having interconnected front, rear and side walls spaced inwardly from the corresponding vside walls of the casing to form downfiow paslevel fuel control valve located within said casing near the connection of one of the downow passages with a secondary passageway for control ling fuel supply to the burner.

3. A liquid fuel burning furnace including a i casing having interconnected front, rear and side Walls connected by a bottom, a jacket having interconnected front, rear and side walls spaced inwardly from the corresponding side walls of the casing to form downow passageways with the lower edges of said walls spaced from said bottom, a. heat absorbing jacket having walls conforming to the first named jacket and spaced inwardly therefrom to provide secondary air passageways between the jacket walls, said pasysageways being connected with the downow passageways by reason of said spaced lower edges, a heating unit supported within said heat absorbing jacket, and a constant level fuel control valve located in one of the downilow passages near the connection thereof with a secondary passage for controlling fuel supply to the burner.

4.' A liquid fuel burning furnace including a casing having interconnected front, rear and side walls connected by a bottom, a. jacket having interconnected front, rear and side walls spaced inwardly from the correspondingv side walls of the casing to form downflow passageways` with the lower edges of said walls spaced from said bottom, a heat absorbing jacket having walls conforming to the first named jacket and spaced inwardly therefrom to provide secondary air passageways between the jacket walls, said passageways being connected with the downow passageways by reason of said spaced 'lower edges,

a. heating unit supported within said heat absorbing jacket, and a constant level fuel control valve located in one of the downiiow passages and'above the wall of the jacket which forms said passage for controlling fuel supply to the burner, nussm'mn'rm.

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