US2357831A - Hot-air furnace - Google Patents

Description

P 1944. R. L. JUDY 2,357,831

HOT AIR FURNACE Filed May 19,- 1941 Gttornegs Patented Sept. 12, 1944 UNITED STATES PATENT. OFFICE HOT-AIR FURNACE Ralph L. Judy, near Kirkland, Wash.; Myrtle M. Judy executrix of said Ralph L. Judy, deceased Application May 19, 1941, Serial No. 394,177

4 Claims.

My invention relates to a novel furnace construction, particularly -well adapted for incorporation in domestic heating furnaces of the hot air type, and is equally advantageous where air conditioning equipment is employed in the system.

In most furnaces for use in home heating, which heat air to be recirculated through the house, the heating efficiency of the construction employed is quite low. Various expedients have been tried for increasing the efficiency of such installations with greater or less success, but in most cases it was found that where the cost of the construction was not prohibitive from a commercial standpoint only a very small increase in efficiency was obtained.

Further diificulties were also experienced in such structures in that certain parts would tend to become overheated and burn out quite rapidly, and the structures providing an intricate maze of heat transfer passages were very difficult to clean or repair, as Well as being expensive to construct. As a result, a high efficiency hot air heating plant for domestic use has not been available at a reasonable cost.

In general my construction includes a furnace casing having a combustion chamber in its lower portion which is fired preferably by an oil burner of the pressure atomizing or injection type, although other fuels and burner types may be used instead as the heat source. Above this combustion chamber are arranged two sections of generally horizontal heating tubes, interconnected by headers so that the hot combustion gases pass from the combustion chamber to the lower set of radiating tubes in one horizontal direction, and then in the opposite direction through the upper set of heat radiating tubes, to pass out the flue.

The air to be heated for recirculation through the house enters the lower portion of the side of the furnace casing immediately above the combustion chamber and in the zone occupied by the lower set of heating tubes. The entering air is thus warmed by heat radiated both from the roof of the combustion chamber proper and from the heating tubes themselves. The air, after passing generally horizontally about the lower set of heating tubes, flows upward into the chamber housing the upper set of heating tubes, about which it also passes in a generally horizontal, but opposite, direction, and then passes out through the air discharge outlet from the furnace casing. Thus both the combustion gases and the air to be heated pass upward through the furnace caspreferably disposed mutually transversely, and intersect each other.

Damper mechanism is provided to regulate the flow of combustion gases so that the volume of such flow will be approximately equally distrib uted through all the heat radiating tubes of each set. All the tubes, therefore, can operate with the same efficiency.

The principal object of my invention is to provide a furnace of simple and inexpensive construction which nevertheless will afford unusually great efficiency, and to provide such a construc tion which will be suitable for use in furnaces burning any of the customary types of fuel. Such general object is primarily to be accomplished by greatly increasing the heat radiating surface within the furnace casing by a simplified heat exchange construction, and constraining movement of the air to be heated to intimate contact with such extensive heat radiating surface.

Another object is to provide such a construction which will be readily accessible for cleaning of the parts which might tend to accumulate soot, and it is also an object to provide proper damp ers or equivalent control means for equalizing the flow over the heat-radiating surfaces, thus to discourage deposit of soot on them, as well as to increase generally the heat transferring efficiency of the furnace by equalizingthe temperature differential between the combustion gases and the air to be heated throughout each of the several heating zones. 7

Still a further object is to provide a construction in which the air to be heated, as well as the combustion gases, will traverse a tortuous path between and aroundthe heat-radiating surfaces in such a manner that each portion of the air flow will travel approximately the same distance in its circuit as the other portions of the air flow, thus tending to equalize distribution of the heat absorptive medium, and to obtain substantially uniform flow velocity throughout such passage. It is intended, however, that the airconnections be such that an air conditioning system can be employed conveniently in conjunction with the furnace. V

Other objects of my invention and important characteristics of the construction and operation of my furnace will be presented in the following specific description of the representative furnace construction illustrated in the drawing.

Figure 1 is a. vertical longitudinal section through the furnace, taken along line l-l of Figure 2, while Figure 2 is a vertical transverse secing in Shi -91 pentine p ths, which are tion along line 2-2 of Figure 1. i

Figure 3 is an end elevation view of the upper portion of the furnace, showing part of the casing broken away to expose the internal furnace structure.

Figure 4 is a fragmentary side elevation view to an enlarged scale, showing damper-operating mechanism.

In general the furnace consists of a casing I 7 within which is located a generally horizontal partition ID forming the roof of the combustion chamber As previously mentioned, any of the customary fuels can be used for heating in my furnace, but I believe that the best results can be obtained by the use of oil, and consequently I have illustrated the pressure atomizing or injection type of oil burner I I, which projects into the combustion chamber through an aperture I2 in the front of the furnace casing Preferably the partition ID terminates forwardly or short of the back wall of the furnace casing I, as shown in Figure 1, leaving an upwardly extending shaft or cavity defined by a generally vertical forward wall I3 and by anupright rearward wall I4, which may be inclined or curved rearward and downward in the manner shown. The top of this cavity is closed by qne'er d of a second horizontal partition I5, which will be described more fully later, to form, with the portion of the casing beneath partition 10, a generally L-shaped combustion chamber with a horizontal leg and an upright leg. In order to enable the combustion chamber to be cleaned'out readily an aperture I6, closed by a door I'I, may be provided in therear wall of the casing I. Such. a clean-out door "may be hinged, or otherwise supported in any suitable I manner.

Above the combustion chamber are located two additional p eltitions, one a vertical partition 2 near the front wall of the casing I, and extending upward from the lowest horizontal partition I0, and the other another horizontal partition 2|] above I and located near the top wall of the casing. These two partitions meet near the top front edge of the furnace, and partition I5 is joined to the central portion of partition 2. Partition |4 extends upward from its junction with partition I5 substantially parallel topartitions 2 and I3, and is also joined to partition 20; Preferably the portion of partition I4 above partition I5 is spaced approximately the same distance from the back wall of the casing I as partition 2 is spaced from the front casing wall.

Extending generally horizontally between up-.- right partitions 2 and I 3 and substantially equally spaced from each other and from partitions IOand I5 are horizontal heating tubes 2| which communicate both with the upright leg of the generally L-shaped combustion space in the lower portion of the casing and. with the front header or manifold chamberbetween the front wall of casing and partition 2. The inclined portion of wall I4 serves to deflect the combustion gases from such upright leg into the enter? ing end of these tubes. A similar but slightly longer set of tubes 22 extends between the; upper portions of partitions 2 and I4, the tubes being approximately equally spaced from each other and-from the horizontal partitions l5 and 20. It will be evident that the number of tubes 2| and 22 in each set may be varied, as can the size and wall thickness of each tube, the selectionof these factors depending upon the type of fuel being burned,the heating capacity'of the furnace, the length of the tubesQth'eir relative spacing, and other considerations which may be involved in determining the best design for particular installations and operating requirements.

A flue 23 is connectedto the rear header or manifold chamber between partition I4 and the rear wall of the furnace, while immediately below the flue connection a second clean-out aperture 24 is provided, normally closed by a door 25, affording access to this header space for cleaning purposes, to be described more fully hereafter. The flow of through this header to the flue may be controlled by a damper 26 journled on a rod 21. Any suitable means can be employed for swinging and holding this damper in the setting to afford the desired operation. Such means may conven-' iently be an arm 28 secured by one end to rod 21 and having its other end apertured for con-' nection to an arcuate plate 29 by a pin inserted through it and into the appropriate one of the e a h le r u plate,v t reta n damp in the proper swung position. V

And to be heated for recirculation through the dwelling is supplied through a conduit 3 connected to the side of the furnace casing, in which ma e p de p e ans, f rs, a humidifying equipment to condition the air before it is heated. The air thus admitted takes the sinuous upward course transversely ofthe furnace casing indicated by the arrowsin Figure 2, being discharged through, opening 30, The portion of partition I5 between wall I3 and wall I4 extends completely from side to side of the furnace casing, so that no combustion gases are admitted to the air space but all are compelled to flow through tubes 2| inthe direction indicated by the arrows in Figure 1 for exit from tend completely from side to side of the casing, 1

and only betweenpartitions 2 and I4 in a space left between an edge of partition 20 and a side wall of the furnace casing through which air may pass to the outlet .3

In Orderthat'sootmay be removed readily from tubes 2| and 22 clean-out apertures I8, one registering with each tume, are provided in the front wall of the furnace casing 'I, each covered by an individual plate I9, removably'secured in place by screws or equivalent means; Instead of providing a separate aperture for each tube it will be evident that asection of the front casing Wall between partitions I0 and, 20 and of a width suflicient to expose the, ends of. all the heat-radiating tubes might be made removable.

A suitable cleaning brush can then be pushed through each tube from its end projecting through partition 2 the soot from tubes 2| being pushed rearwardly .downi-nto the combuscombustion gases The efificient heat exchange capabilities of my furnace will be readily recognized. The combustion gases give up heat to the air entering intake 3 through the roof III of the combustion chamber itself. They then pass upward to the fiue outlet in a sinuous or serpentine path of generally S-shape, first into the cavity between walls I3 and I4 forming the upright leg of the L-shaped combustion chamber. Here an additional amount of heat is radiated to the air through the wall '13 and the roof I5 before the gases pass horizontally into the tubes 2l.- Next heat is radiated from them through the tube walls to the air flowing about the tubes until the combustion gases pass into the forward header. As they again rise heat is radiated through wall 2 and the roof 20 of this compartment until the combustion gases pass again horizontally but in the opposite direction into the upper set of tubes 22. Through their walls heat is radiated to air circulating'about these tubes until the gases pass into the rear header. From this chamber the final remainder of heat which can be effectively removed from the combustion gases is transmitted to the air through the roof portion formed by part of partition 26 and through the upper part of Wall M, because the combustion gases now must move downward for discharge into flue 23. The sinuous path traversed by the combustion gases is therefore such that they come into intimate contact with a very large amount of heat absorbing surface.

Not only are such surfaces arranged so that heat can be picked up by them readily from the combustion gases, but the airflow on their opposite sides is such that the heat radiated by them can be removed by the air to best advantage. Thus the coldest air will pass generally horizontally into the side of the furnace casing through the lower portion of duct 3 ,and immediately across the roof ll] of the combustion chamber, so that a maximum amount of heat can be transmitted to it during such travel and such roof will simultaneously be prevented from over heating.

The air thus warmed will pass around and over the surfaces of tubes 2|. While these have been shown in registry they may be arranged in staggered relationship to increase the turbulence and deviation of air flow, if desired. Ordinarily, however, this is unnecessary, and might tend to create excessive resistance to passage of air through the furnace.

From the heating zone of pipes 2| the air will pass upward around the edge of partition [5 as shown in Figure 2 into the heatin zone of pipes 22, where it will flow generally in the opposite horizontal direction about and over the surfaces of these pipes. The air then flow upward around the edge of partition 20 for exit through duct 30. During its transit through the furnace, therefore, from duct 3 to duct 30 the air has traversed an S shaped path, so that the air on the inside of one curve of such path will be on the outside of the next curve, and vice versa, causing the column of air to move with substantially uniform average velocity in all its parts. At the time of its passage through the tube chambers the air will also, of course, pick up a certain amount of heat radiated from the end walls l3, I4, and 2, as well as from the portions of horizontal partitions I5 and 20 previously mentioned. In the latter case the heat will be conducted toward the center of these partitions for better distribution of the heat to the air.

sinuous, generally S-shaped path crosswise 'of the furnace mentioned above, the combustion gases will move through a sinuous, generally 8- shaped path lengthwise of the furnace, as previously described, composed of the combustion chamber, the cavity at the back of the furnace, tubes 2|, the header cavity at the front of the fur.- nace, and tubes 22. These two paths will thus be disposed in mutually transverse, intersecting relationship.

Depending on the proportions of th various parts, as well as on their relationship to each other, it is probable that the flow through the upper and lower rows of tubes 22 will not be equal. In order to maintain as far as possible a uniform temperature differential between all the tubes 22 and the air in that chamber, and in order to reduce the temperature of all portions of the air entering flue 23 to the same value, I provide the damper 26, which may be adjusted from the vertical or even from a rearwardly swung position into the forwardly swung position shown in broken lines in Figure 1. The holes provided on the'curved plate 29, shown in Figure 4, will enable the damper operating arm 28 to be set in any selected one of a large number of positions, so that the angularity of damper 26 in the header chamber at the rear of the furnace may be adjusted with accuracy and maintained in such adjusted position. Under ordinary conditions it will probably be necessary to swing the damper plate slightly forward on its hinge rod 21 so that a freer flow will be provided through the slightly longer path of the upper row of tubes 22 than through the lower row. As a result the velocity and quantity of combustion gas flowing through each tube 22 should be equal to that flowing through each other such tube. It will be understood that conventional draft doors and dampers will be provided as usual in addition to damper 26 for controllin the combustion within the combustion chamber.

What I claim as my invention is:

1. In a heating furnace, a casing defining a combustion chamber in the lower portion thereof, a lower group of generally horizontal heating tubes extending lengthwise within said casing and having one end communicating with the'combustion chamber, an upper group of generally horizontal heating tubes extending lengthwise within said casing, means interconnecting the other end of said lower group of tubes with one end of said upper group of tubes, a flue communieating with the other end of said upper group of tubes, both said upper and lower groups of tubes being spaced a substantial distance from both side walls of said casing, a generally horizontal baffle plate between said upper and lower groups of heating tubes, spaced a substantial distance from While the air to be treated is traversing the both tube groups, projecting from a side wall of said casing. across the entire width and length of said lower group of tubes and having a free edge spaced from the opposite side wall of said casing to leave a passage therebetween, an air inlet duct connected to the side of said casing from which said baflle plate projects and between said Plate and the combustion chamber for directing air to be heated generally horizontally transversely across the outer surfaces of the heating tubes in said lower group, and upward past the free edge of said baffle plate, means below the top of the casing and spaced a substantial distance above the upper group of tubes, guiding such air for flow thence transversely acros the outer surfaces of the heating tubes in said upper group, and an air 'outlet ductconnected to the upper part of said casing for receiving the air heated during; such passage.

necting the other end of said lower group of tubes with one end of said upper group of tubes,

a flue communicating with the other end of said upper group of tubes,both said upper and lower groups :of tubes being spaced at siibstantialdistance from both side Walls of said casing, an upper generally horizontal baflle plate above said upper group of tubes, projecting from one side wall-of said casing across the entire width and length of said upper group of tubes and having a free edge spaced from the opposite side wall of said casing to leave a passage therebetween, a lower generally horizontal bafile plate between said upper and lower groups of heating tubes, projecting from the side wall of said casing opposite that from which said upper baffle plate projects across the entire width and length of said lower group of tubes, and having a free edge spaced from the casing side wall opposite that from which it projects to leave a passage therebetween, an air inlet duct connected to the side of said casing from which said lower baffle plate projects between it and the combustion chamber, for directing air to be heated generally horizontally transversely across the outer surfaces of the heating tubes in said lower group, then upward past the free edge of said lowerbaille plate, then transversely across the outer surfaces of the heating'tubes' in said upper group, and then upward past the free edge of said upper bafile plate, and an air outlet duct connected to said casing above said upper 'bafile plate for receiving the air heated during such passage,

3. In a heating furnace, a casing defining a combustion chamber in the lower portion thereof, a lower group of generally horizontal heating tubes extending lengthwise within said casing and having one end communicating with the combustion chamber, an upper group of generally horizontal heating tubes extending lengthwise Within said casing, a common header interconnecting the other end of said lower group of both said upper and lower groups of tubes being spaced a substantial distance from both side walls of said casing, an upper generally horizontal 'baflie plate above said upper group of tubes, projecting from one side wall of said casing across the entire width and length of said upper groupof tubes and having a freeedge ass-7,831

the entire Width and length of said lower group of tubes, and having a free edge spaced from the casing side wall opposite that from which it projects to leave a passage therebetween, an air inlet duct connected to the side of said casing from which said lower baffle plate projects between it and the combustion chamber, for directing air to be heated generally horizontally transversely across the outer surfaces of the heating tubes in said lower group, then upward past the free edge of said lower baflie plate, then transversely across the outer surfaces of the heating tubes in said upper group, and then upward past the free edge of said upper bafile plate, an'air outlet duct connected to said casing above said upper baflle plate for receiving the air heated includingan upper row and a lower row extending lengthwise within said casing and having one end communicating with the combustion chamber, a flue header having the other end of i said group of tubes connected to one side thereof, an air inlet duct connected to a side of said casing for admission of air to be heated, means within said casing guidingsuch air forflow transversely across the outer surfaces of all the heating tubes in'said group, an air outlet duct connected to the upper part of said casing for receiving air thus heated, a flue connected to the side of said flue header opposite that to which said group of tubes is connected, and at a location below such connection of the lower row of heating tubes in said group, a horizontal pivot rod journaled in said flue header substantially midway between the header sides towhich said tubes and said flue are connected, andat a level substantially midway between said upper and lower rows of heating tubes in said group, and a flow equalizing damper depending from said pivot rod,'inoperative to stop. flow through any of said tubes, but. swingalble by said rod to vary the relative cross-sectional area of the paths across said flue'header from said upper row of heatingtubes and from said lower row of heating tubes, respectively, to said flue.

RALPH L. JUDY.

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