US1873767A - Heating stove - Google Patents

Description

Aug. 23, 1932. KAHN I 1,873,767

HEATING STOVE Filed 001;. 8, 1930 2 Sheets-Sheet 2 gnuwntoa anoint Patented Aug. .23, 1932 umreo STATES PATENT. oF'ri-cE nnnrnmn ammo); cmcnnu'rr, onro, ASSIGNOB 'ro THE ESTATE STOVE courm, or mnrou. .oruo, A conrona'rrou or 01110 1 nm'rme srovn. 7

Application filed October a, 1930. Serial K0. aaaaio.

This invention relates to heaters, and more particularly to portable heaters of the convection type.

One of the principal. ob'ects of the inven- 5 tion is to provide such a eater with means for increasing the effectiveness and efliciency of the transfer of heat energy into the circulated air during operation and for increasing the life of the heater,'and its ability to withstand abnormally hard operation.

Another object of the invention is the provision in such a heater, of an air heating duct of high thermal conductance, in.which the exterior surface is the heat absorbing surface, and the interior, heat transferring surface, has substantially greater area than the exterior absorbing surface. 7

Other objects and advantages of the invention will be apparent from the following description, the attached drawings and the appended claims.

In the drawings, which disclose a preferred embodiment of the invention,

Fig. 1 is a vertical sectional view of a heater constructed in accordance with this invention; and

Fig. 2 is an enlarged view, partly in section, of the air heating duct.

Referring now to the drawings, in which like characters of reference designate like parts throughout the several views thereof, the invention is shown and described as embodied in a portable heater of the convection type adapted to utilize coal or other solid fuel, such as is adapted for use in a living room or the like to heat the air therein primarily by convection. A heater of this character is such a one as is sold under the mark Heatrola. The heater comprises generally an inner structure within which a fire may be maintained,'and an enclosing casing in which suitable openings are provided for the passage of air to be heated by contact with the heated walls of the enclosed and enclosing structure. An air heating duct is associated with the enclosed structure to provide an efiicient means of heat transfer and to thereby increase the circulation of air through the heater. The heater .comprises a base member 10 having suitable supporting feet 11; the base providing asupporting means for the enclosing cas ng, and also-for the enclosed or inner heating structure which comprises an ash box 12 which, as shown, 1

may be formed as an integral part of the base 10 or may be a separate piece attached thereto by suitable means. The ash box has mounted upon it a fire-pot 1 1; a suitable grate 15 being provided therein for the support of a fuel bed. A combustion chamber 16 is provided by an enclosing member 17 which is attached to the top of the fire b0x as by means of bolts 18; a suitable flue outlet 19 being provided adjacent thetop of the combustion chamber 16. The exterior of the combustion chamber casing 17 carries' ribs 20, and similar ribs 21 are on the exterior of the fire-pot 14 to facilitate the trans.- fer of heat from the hot walls-of the heating structure to air which is adapted to circulate over the outer surface of this structure. enclosing casing comprises vertically extending walls 22 suitably joined, and supported at 23 upon the base 10. The casing walls 22 are suitably spaced from the heating elements to provide an air space or flue 25 throu h which air may pass upwardly, being heate as it passes in contact with the heated walls of this air circulating space. The casing walls are provided with a plurality of louvers 24 adjacent the base 10, which admit air into the circulating space, at the same time preventing [direct outward radiation from the heating structure while allowing a certain amount of radiation downwardly to warm the floor around the heater. Air which is heated within the area 25 rises and passes from the heater through a perforate cover member 26 suitably supported by the members 27 the cover providing a cap for the casing walls 22 and providing an outlet for the heated air through a plurality of openings 28 of sufficiently large proportions to permit of rapid egress of large quantities of rapidly moving air therethrough, tothus create a circulation of high veloclty so that the heated air has the power to travel through a large area such as an entire house, which may be thus effectively heated and maintained at a uniform temperature.

The

i To provide for additional transfer of heat from'the hot products of combustion'w-ithin the combustion chamber 16 to the air passing through the ace25 an air heating duct 30 .is provided within the upper-portion of the combustion chamber 16 ad acent the flue outlet 19 through which heated air from the space 25 may pass to be further-heated by contact with the hot inner surface of the walls of the duct and be then discharged through the ro es of theheater at relatively high velocity. The air heating duct 30 in-.

creases the heating effect upon the circulatin air, and correspondingly iIICREaSGS the ive ocity of the air passing through t e' heater and so greatly increases the rate of circulation thereof and accelerates the circulation of air through the room.

As shown the air heating duct 30 comprises a hollow inverted substantially T -shaped metallic casing made preferably as an iron casting, and which is directly exposed to the hot products of combustionin the interior of the combustion chamber. The duct 30100111- rises oppositely extending open-ended branches 31 which project through openings 32 in the side walls ofthe combustion chamber casing 17 and open into the area. 25, and an open-ended upstanding portion 33 which is attached within the top of the combustion chamber adjacent an opening 34 provided therein. Air which enters the branches olding bolts 39 which pass through the casing 17 and are adapted to'hold the air heating duct 30 in position with respect} to the combustion chamber. A suitable sealing material, such as cement, may be inserted in the space 40 between the rim 35 and the engaging rim 36 to provide a gas tight joint.

' 'table sealing means are also provided be tween the. pro ectin ends of the air duct branches 31 where t ey extend through the openings 32 in the side walls of the combustion chamber casing 17 'As shown, the sealing means at each opening 32 comprises tworing like members which loosely encircle the duct end 31, the inner ring 42 being provided with an annular depression 43 which is adapted to receive suitable packing material such as asbestos rope, while the outer ring 45 l is ada ted to overlie the rin 42 to com ress I fies g P theas tos rope in the groove 43 against the duct and provideatight but resilientj oint with the surface of the duct end 31. The rings 42 and 45 are provided with attaching means such as the similarly positioned ears 47 havingopenings through which bolts 48'pass for the attachment of the rings to the combustion chamber. In assembling the sealing rings the contacting surfaces between the rings and the combustion chamber may be cemented so that upon drawing the bolts 48 up tight, gas tightstuffing boxes will be provided within which each end 31 ofthe air duct may freely expand and contract under the influence of temperature change Without placing any strains on the structure itself.

The duct 30, being positioned within the combustion zone,- is subjected to very high temperatures. The lower portion is positioned so. that the flames of combustion impinge directly thereon. The upstanding portion 32 of the duct is positioned in the top of the combustion chamber and adjacent the flue, but it too is subjected to high temperatures and highly heated products of combustion. As a result the duct absorbs largev quantities of heat energy on its outer absorbing side which it transfers to the air currents passing therethrough. The duct therefore not only increases the efficiency of the heater by increasing the rate of air circulation but also provides an economy of fuel consumption by transferring to useful purpose heat which would otherwise be wasted by being discharged from the flue. The interior or heat transferring surface of the duct is formed to have an area for contact with the air which is greater than the exterior heat absorbing surface of-the duct. As shown, the interior surface 50 of the air duct is provided with V-shaped ribs positioned substantially transversely to the flow of air through the duct; the outside surface being left smooth:

As-shown the ribs in the several parts of the duct are differently directed, the ribs in the body portion being angularly arranged with respect to ribs in the branches, the ribs in the various parts of the duct being thus all positioned transversely to the path of the circulating air. The proportions are such that the interior heat transferring or radiating surface is of greater area than the exterior heat absorbing surface, whereby the transfer of heat from the products of combustion to the interior surface of the duct and thence through the duct and into the air passing thereover is accomplished with greatly mcreased effectiveness.

The duct 30 is positioned to be impinged on by the very hot products of the combustion. Itis not unusual for ducts of the character previously sometimes used to be heated to incandescence, to-temperatures of the order of 1300 F. By the use of this invention, using a preponderating heat transferring surface, the absorption of heat I creasing the conductivity as tocause rapid burning out of the duct. However, in-th1s invention due to the increasedheat transfer 1 T creases, at

tial across the duct wall. This results in a material increase in heat transfer and, at the same time, a decreased temperature of the duct wall itself. The thermal conductivity of iron decreases as the temperature temperature of the duct would ordinarily have reached red heat under r thus result, especially under severe condl f tions of heavy load, would result in so dethe temperature of the duct walls is kept down by the rapid transferring ofthe heat absorbed so that the wall temperature will not reach a point which will inefiicient' transfer of heat or resu ing down from overheatin the natural inefliciency o the material at high temperatures which, in the case of iron at 1300 F. produces red hea't, volumes of air passing over red hot iron causes a rapid oxidation of the surface and quickly forms a resistin coating which further and permanently ecreases the heat transferring capacity of the duct; an'dwill cause burning out of the duct. j

While the form of ap aratus herein described constitutes a preferred-embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims. 7 What is claimed is: 1. In a heater of the character described, in which a combustible fuel is burned within a combustion chamber, and convection air is passed over heat transferring surfaces heated by the combustion within said chamber; an air heating duct having an exterior heat absorbing surface positioned within the path of the heated products of combustion to receive heat ener therefrom, and an produce an t in breakinterior heat transferring surface positioned in the path of travel of the air being heated and in heat energy transferring relation with said traveling air, said heat transferring surface being formed of closely positioned corrugations to resent an efiece tive heat transferring su'r ace which is of greater extent than the said heat absorbing surface, and forming with-the heat absorbing surface a substantially uniform path of conduction.

2. In a heater of the character described,

red heat having become almost negligible; and in previously used ducts the;

ther heavy. draft. The high temperature wh h would In addition to a combustionfchamber,and convection air is passed over heat transferring surfaces heated b the combustion within saidchamber; an air heatin duct having anexterior heat in which a combustible fuel is burned within I absorbing s'ur ace ositioned within the path of the heated pro uctsofcombustion to receive heatenergy the'r'efrom,'and an interior heat -transferrin "surface osi'tioned in the traveling air said heat transferring surface being forme ofclosely positione shallowcorrugations to present a grooved-interior aside n efl'ective heat transferringsur absorbing surface, and to form with the heat absorbing surface a heat conduction wall in which the path of maximum len h doesnot substantial y exceed the path 0 conduction of minimum length.

3. In a heater of the character described, in which a combustible fuel is burned within acombustion chamber, and convection air is passed over heat transferring surfaces heated by the combustion within said chamber; an air heating duct having an exterior "heat absorbing surface positioned within the'path of the heated products of combustion to receive heatenergy therefrom, and an interior heat transferring surface .positioned in the path of travel of the air being heated and in heat energy transferring relation with said traveling air, said heat transferring surface being formed of closely positioned corrugations to present a path of travel 0 the air bemg heated and in cat energy transferring relation with said heat transferring surface constructed to pro-.

whichis of greater extent than the said heat 7 grooved interior heat transferring surface,

greater extent than the said heat absorbing surface.

4. In a heater of the character described, 1

in which a combustible fuel is burned within a combustion chamber, and convection air is passed over heat transferring surfaces heated by the combustion within said chamber; a curved air heating duct having a smooth exterior heat absorbing surface positioned within the path of the heated products of combustion to receive heat energy therefrom, and an interior heat transferring surface positio'nedin the path of travel of the air being heated and in heat energy transferring relation with said traveling air, said heat transferringsurface being formed of closely positioned shallow corrugations to present a'grooved interior heat transferring surface, the grooves and intermediate ribs in the several parts of the said interior surface-being arranged angularlywith respect and substantially transverse to the direction of air flow therethrough, the said duct being constructed to provide an effective heat transferrin surface which is of greater extent than t e said heat absorbing surface.

5. In a heater of the character described, in which a combustible fuel is burned within a combustion chamber, and convection air is passed 'over heat transferring surfaces heated by the combustion within said chamber; an air heating duct for the most part of v substantially tubular cross section and comprising a wall of substantially uniform heat conducting characteristics, said duct having a body portion and laterally extending branches, and having an exterior heat absorbing surface positioned within the path of the heated products of combustion to receive heat energy therefrom, and aninterior heat transferring surface positioned in the path oftravel of the air being heated and in .heat energy transferring relation with said traveling air, said heat transferring surface being formed of circularly extending closely positioned shallow grooves to present an effective heat transferring surface which is of greater extent than the 'said heat absorbing surface. v

In testimony whereof I hereto afiix my signature. v

BERTRAND B. KAHN.

Images