US1921817A - Domestic heater - Google Patents

Description

H. A. GRINE 1,921,817

DOMESTIC HEATER Filed Jan. 20, 1935 2 Sheets-Sheet l /2 EINVENTOR. "/A/P/PJ A GlP/A A,

- 5 f ATTORNEY.

H. A. GRINE DOMESTIC HEATER Aug. 8, 1933.

2 Sheets-Sheet 2 INVENTOR.

Filed Jan. 20

ATTORNEY.

Patented Aug. 8, 1933 This invention relates to attachments for use in coal burning domestic heaters to adapt them for efficient oil burning or underfeed coal stoker Coal furnaces for domestic heating of either a hot water or steam type are designed for operation with relatively deep fire beds. mal operation the coal fire a domestic furnace gives oif its heat units continuously at a relatively slow rate and because of the large area of fire which is in contact with the heating sure furnace, a large portion of the heat is transmitted directly to the surrounding heating surfaces by conduction. The relatively slow flow of air through the firebed even when the drafts are wide open permits the transfer of a considerable amount of heat by convection although the furnace may be provided with relatively short combustion gas travel. ant heat of a coal fire accounts for only a portion of the total heat evolved, even when the furnace is being forced.

In the past oil burning and underfeed coal stoker equipment has been installed in domestic heaters designed for hand firing with coal. results have been unsatisfactory in many regards, particularly from the point of view of efficiency. An oil burner, in contradistinction to a coal fire. gives off heat at a very rapid rate and is operated for short periods of time only. Such equipment is normally provided with a blower creating an air blast which atomizes the oil the combustion gases pass through the furnace at a higher rate of speed so that the transfer of heat convection is inefficient. Since the flame in most designs is not in contact with the side heating surfaces of the furnace practically no heat is transferred by direct conduction and in fact a very large proportion of the heat absorbed from the oil flame is in the form of radiant heat which is of course, only a minor part of the total heat evolved in any equipment which pretends to complete combustion of the oil. As a result excessive high stack temperatures result and a considerable portion of the heat evolved is wast--- ed up the stack.

The low efficiency of oil burning equipment in domestic furnaces designed for burning coal has lead to the construction of special oil burning heaters in which the gas travel is lengthened and the amount of heat absorbing surface is very greatly increased in order to permit absorbing the heat of the oil name during the intervals when the oil burner is operatin and as a result the gases by These special w en ATEN'E" @t'FlQE Usrrso srares DOMESTIG HEATER Harry A. Grine, White Plains, N. Y.

Application January 20, 1933. S rial No. 652,612

(Cl. i222l0) furnaces have also been provided with a larger number of passes more closely spaced than in the case of coal fired equipment, and the high velocity of the gases ri'ven by the air blast of the burner results in suiiicient turbulence so that all portions of the gas stream come in contact with the water cooled heat absorbing surfaces and give up their heat by convection.

Special oil burning furnaces are expensive because they require an entire new installation and the coal burning furnaces have to be scrapped.

It has been proposed to slightly increase the efficiency of oil burning equipment by placing a disc or other small baffle or deflector over the burner, the baffle usually being constructed of fire brick. This attempt to improve the efficiency of oil burn ing equipment applied to coal fired domestic furnaces does to some extent, increase the turbulence of the combustion gases and deflecting them to some extent against the side walls of the heater. At the speed with which the gases are driven through the furnace, the amount of heat which is transferred by convection is still too low for efficiency because of the short gas travel and particularly the insufficient heating surface. The most serious lack in a fire'brick deflector disc or baflie lies in the fact that it does not add any additional heat absorbing surface and the improvement which it effects consists solely in a somewhat better utilization of a part of the heat absorbing surface already present in the boiler. Even the slight increase in heat absorbing efiiciency which is effected by the use of fire brick bafiies is at the expense of some loss of radiant heat which is reflected down to the bottom of the ash pit and results in a higher ash pit temperature and therefore greater heat losses through the ash pit walls which are normally not Water jacketed.

The present invention provides the required additional heating surface needed to absorb heat I at the higher rate at which it is evolved in an oil burner, assures sufficicnt length of gas travel and turbulence to efficiently absorb the heat of combustion gases and permits a low stack temperature with the corresponding increase in efficiency in utilizing the heat units of the oil. The objects of the invention are effected without the necessity of any dismantling of the coal burning equipment other than that required for installation of the oil burner, and the added members are simple and cheap in construction and can be installed with a minimum of labor.

Essentially the present invention consists in hollow members which are inserted through the fire door of the furnace and so disposed as to add an additional pass to the furnace. The problem of installing a satisfactory heating surface through the fire door is a difficult one because the fire door is normally by no means as wide as the corresponding section of the fire box and a small heat absorbing member is but little better than a fire brick deflector because the gases flow rapidly around it without being forced into contact with the water cooled walls of the boiler itself. According to the present invention the auxiliary heating surface is formed in two or more units, each of sufhciently less width than the fire door to be inserted therethrough, but when fitted together substantially extend across the whole of the fire box area so that they constitute a true additional pass to the boiler. The assembled units are of a total width substantially equal to that of the fire box, but are shorter in a fore and aft direction so that the combustion gases from the oil burner flow up over the forward or rear end depending on the location of the opening to the next higher pass.

A further important advantage of the present invention lies in the fact that the additional heating surface coupled with the improved utilization of the heating surface already present in the boiler by reason of the bailiing effect, very markedly increase the capacity of the boiler. Not only does this permit efficient operation of an oil burner but it remedies the difficulty of inadequate boiler size which is frequently encountered in houses which have been built to sell and in which the heating system has been skimped by using a boiler of inadequate capacity. To such installations, the present invention not only presents the advantages of eificient oil burner operation but it so increases the capacity of the boiler that the inadequacy of the system is remedied.

It is necessary to assure a satisfactory rapid circulation of water through the auxiliary heating surfaces particularly since its heat absorption is relatively high, in fact, higher than any other portion of the heat absorbing surface of the furnace because it is located immediately above the flame of the burner and hence, absorbs the full radiant heat. At the same time water must enter and leave through the fire door opening or through the small holes which are normally provided in the water jacket for the insertion of heating coils of domestic hot water systems. It is a special advantage of the preferred embodiment of the invention that an extraordinary rapid fiow of water and uniform distribution is obtained by the special design of heat absorbing elements which will be illustrated.

It is a further advantage that in the preferred designs, water flows into the auxiliary heat absorbing elements through pipes which can be connected to the hot water or steam pipes at the top of the heater and the cold water return or condensate pipes at the bottom of the heater through ordinary pipe fittings requiring no special equipment and permitting rapid assembly with a correspondingly low installation cost.

Another feature of the preferred design of auxiliary heating surfaces is that they have relatively thin walls which may be made from welded sheet metal since the auxiliary heating surface is flexibly supported in the furnace and is not subject to difierential warping or other stresses which require the relatively heavy walls of the furnace proper. The thin sheet steel construction is not only highly economical, but also permits an extremely rapid heat transfer which is particularly effective since the lower portions of the auxiliary surface are situated where they absorb most of the radiant heat of the flame. In fact in many installations the auxiliary heating surface, although small in area compared with the total heating surface of the boiler, may actually absorb almost as much or actually more heat than the rest of the boiler.

Another advantage of this particular modification of the invention as especially adapted to a common type of sectional boiler lies in the fact that by a peculiar shape of the upper surfaces, the gases are deflected into contact with the side walls to a very marked degree, thus not only adding heat absorbing surface of the auxiliary members but greatly increasing the heat absorbing efiiciency of the water jacketed side walls of the furnace which in ordinary installations operate with very low effectiveness by reason of the fact that hot combustion gases are not forced intimately in contact with these surfaces.

In the drawings the invention will be shown as applied to two common types of domestic heaters, a sectional boiler and a typical round boiler. The invention is however in no sense limited to these particular designs of boiler but on the contrary is generally applicable to all coal fired boilers with suitable chan es in the shape of the two auxiliary heating members to conform to the shape of the fire box.

In the drawings the auxiliary heating surface is shown. as fitting tightly against the side walls of the fire box. It should be understood, however, that the essential principles of the present invention are equally applicable to auxiliary heating members which fit loosely against the walls of a fire box. as complete gas tightness is not essential, for if a small amount of gas passes up between the edges of the auxiliary heating members and the fire box walls it is forced inti mately into contact with these walls and the efiicient utilization of the surfaces is therefore preserved. In fact in some designs a small leakage around the edges of the auxiliary member is actually desirable and produces a more satisfactory fiow of heating gases. Where a tight fit is desired, particularly where in the case of common sectional boilers, the inner surfaces are slightly arched, the auxiliary members may be provided with non-uniform edges to conform with the shape of the sections, or the interstices between the straight edge of the auxiliary member and the low points where sections join each other may either be filled in with cement or closed by means of a metal fin which can be welded on to the auxiliary heating member. In the drawings the interstices are shown as filled with cement, a method which is effective in the particular design of sectional boiler as shown, but it should be understood that the invention is not limited to this method of tightening, even with the particular design of boiler shown in the drawings.

In the drawings, Fig. 1 is a side elevation partly broken away, of a sectional boiler.

Fig. 2 is horizontal section through Fig. 1 along the line 22;

Fig. 3 is a front elevation, partly broken away, of the boiler of Fig. 1;

Fig. 4 is a horizontal section of auxiliary member, partly broken, along the line 4- of Fig. 3 looking up from the bottom; and

Fig. 5 is a horizontal section through a typical round boiler.

In the modification shown in Figs. 1-4, the boiler consists of a front section 1, two center sections 2, and a rear section 3; the front section and two center sections being provided. with two water legs, 4 and 5, while the front section is provided with a single water leg, 6, at level 1 the legs 5 of the center sections and the rear section is provided with a water leg 7, at the level of sections l. This design forms two passes above the fire box as shown in Fig. 1, the gases flowiru up at the rear, forward through the first pass, the two fines, and then back, through the second pass, leaving through the stack 8. An oil burner is shown diagrammatically at 9, di recting its flame into. the ash pit 10 which is preferably lined with fire brick. An oil burner of the gun type is shown but it is obvious that any other standard type of oil burner be used or an underfeed coal stoker may be installed. From the fir bricl-z lining which extends up to the bottom of the sections 1, 2, and 3 which normally surround the fire box, relatively narrow columns of fire brick are built up to a level slightly above the lower edge of the fire door. Two of these columns shown at 11 (Figs. 2 and 3) are at the rear corners of the fire box, a somewhat wider column 12 extends up the center of the rear section, while two other columns 13 are located at the rear of the first section. On these columns rest two hollow heating members 14. These heating members, which in the drawings are shown as constructed of sheet steel, are provided with a relatively fiat lower surface 15 which is immediately above the'fiaine of the oil burner and their upper surfaces 16 are arched, being curved over the out fiow pipes 17. The central edges 18 of the heating members are j parallel, and preferably set together to provide a gas tight or substantially gas tight joint. The straight outer edges 19 of the members abut against the points 29 of the arched inner surfaces of the boiler sections. The triangular spaces 21 between the straight walls of the auxiliary heating elements and the thinner portions of the boiler sections are filled in with furnace cement (see Fig. 2).

The auxiliary nl8l'l"blS are water inlet tubes 22 which preferably extend substantially to the rear of the members and are provided with perforations at their sides (see Figs. 3 and 4) so that water flowing in through these pipes is directed laterally along the bottom surface of the auxiliary elements. The out flow pipes 17 are similarly provided with slots in their lower portions and are connected by means of suitable unions 23 to a header 24 from which a pipe extends upwardly to the hot water or steam riser pipes at the top of the boiler. Similarly cold water from the cold water or condensate return pipes of the boiler flows into a header 25 which is connected through unions 26 to the water inlet pipes 22. The particular design of water pipes in the heating elements assures a very rapid and very uniform circulation of water which is essential to satisfactory operation because of the rapidity with which the auxiliary elements absorb heat. This rapid circulation also provided with also prevents local overheating which might recreases in surface exposed to the gases and also results in forcing a considerable portion of the gases into contact with the side walls of the sec tions, thus increasing the effectiveness with which these portions of the boiler absorb W .-ile this design of auxiliary elements combined with the particu .r shape or the sections of the boilers shown inthe drawings result in a very efficient heat absorption, it should be understood In its broader aspects the invention is not limited to the particular design of water inlet outlet tubes illu trated in the drawings but in its preferred embodiment the accelerated flow obtained by the distribution of the water through the openings in the tubes constitutes an additional advantage of the specific embodiment of the invention.

I will be noted that the auxiliary heating members rest on five col mns of fire brick, each member, therefore, being supported at three corners only, although additional support of a flexible nature is afforded by the tubes 1? and 22. Since the auxiliary heating elements are supported only at three corners, they are free to move slightly if differential heating results in any slight temporary or permanent warp ng and there is, therefore, no. danger of break due to strains set up by war; which might a serious problem if they were rigidly supported. This fiexible support of the auxiliary members is an important advantage of the preferred embodiment of the invention, but in its broader aspects, the invention is not limited to this type of support and suitable rigid supports may be employed where desired. In some cases the fire brick columns may be replaced by thin metal legs, thereby preventing the screening of small portions of the heating surfaces by the fire brick. Since however, the heating surfaces in this lower portion of the boiler operate at a relatively low efficiency, the loss by the insulating effect is slight and the fire brick construction has the advantage that it is not subject to warping and softening if the heat is excessive, which might be a factor if relatively thin metal suppor ng legs were employed.

Fig. 5 illustrates the application of the invention to a circular boiler. The shape auxiliary surfaces is, of course, somewhat different in order to accommodate themselves to the shape of the round fire box. The round water cooled fire box wall is shown at 2'7 and the parts of the auxiliary heating elements corresponding to those in Figs. 1 to 4, bear the same members. Because of the relatively short pass horizontally which is a characteristic of a round boiler, it is resent of the the members desirable to increase the eii'ectiveness of the side about by slightly auxiliary heating T1 is construction is not shown in Fig. 5 for the sake of simplicity, but its application is, of course, obvious.

While the present invention is particularly in portant as an auxiliary heating device for ap plication to coal burning domestic heaters which have not been designed for the installation of oil burning equipment, it should be understood that the invention may be applied to specially designed equipment, thus for example, coal burning domestic heaters may be built with shelves or projections on which the auxiliary heating members may best rest, thus obviating the necessity for fire brick columns or metal legs. Designs may also be provided in which the auxiliary members may be hung from rods from the first pass and it should be understood that such suitable modifications of the invention are included, although it is a particular advantage of the preferred embodiment of they invention that it may be applied to equipment which was never esigned for oil burning and without necessitating any structural changes. The design of auxiliary heating surface of the present invention particularly in the preferred embodiment illustrated is distinguished by a great manufacturing economy, for the units are cheap to make and they are so simple and so easily connected to heaters that the cost of installation is unusually low.

The present invention has been described and illustrated particularly in connection with oil burning equipment because the great demand for the installation of such equipment in coal burning domestic heaters renders this field of primary commercial importance. A similar problem, though not quite as acute is presented by various underfeed coal stokers which are installed in many domestic heaters and which employ an air blast resulting in a combustion which has many of the features of an oil burner. The problem is not of as great economic importance with underfeed coal stokers with oil burners because the combustion gas speeds are somewhat lower and because the lower cost of the heat units in the very cheap fine sizes of coal employed in such stoke-rs renders their efficiency of less immediate economic importance. However, although, the waste due to insufficient heat absorption with underfeed coal stokers is not as great as with oil burners, it is nevertheless an important item and, of course, the present invention solves the problems presented by an underfeed coal stoker as applied to a domestic furnace designed for hand ring in precisely the same way as with an oil burner and it should be understood that the present invention is equally applicable to installations in which underfeed coal stokers are used.

What I claim is:

1. In combination a domestic heater of the hot water or steam type having heating surfaces designed for hand fired coal operation and a detachable auxiliary heating surface consisting of a plurality of abutting sections disposed in the fire box area and extending substantially across the maximum width thereof and spaced sulficiently from at least one side of the fire box so as to permit upward passage of the gases through the opening thus formed and constituting an additional pass, each section having its greatest dimensions in a horizontal plane and being of suificiently smaller width than the fire door to permit introduction therethrough and means connecting each section to the water system of the heater at a point below the lowest point of the section and at a point above the highest point of the section, and a fuel burner of the blower actuated type in the ash pit of said heater.

2. A domestic heater according to claim 1 in which the abutting auxiliary heating members are sufficiently spaced from one of the two ends of the fire box so as to constitute a baflle defining with the lowest horizontal heating surface of the heater an additional pass from the combustion gases.

3. A domestic heater according to claim 1 in which the connections from the auxiliary heating members are to pipes in the heating system outside of the heater itself.

4. A sectional domestic heater of the hot water or steam type designed for hand fired coal operation and having a fire box of rectangular section and horizontal fore and aft heating flue passages defined by the sections, in combination with a plurality of abutting horizontally disposed auxiliary heating surfaces of widths sufiiciently less than the opening of the fire door to permit insertion therethrough, but when abutting extending substantially across the fire box area horizontally and fitting substantially gas tightly against one end of the fire box and being spaced from the other end, the spaced portion being at the end opposite to the opening into the lowest flue pass whereby a complete additional pass for the combustion gases is defined and a fuel burner of the blower actuated type disclosed in the ash pit or" the heater, each auxiliary heating member being provided with connections to the upper and lower portions of the water or steam circuit in the heater respectively.

5. A domestic heater according to claim 1 in which the auxiliary heating members rest on supports at not more than three points whereby warping of the individual members by reason of non-uniform heating will not result in strains in the members.

6. A domestic heater according to claim 1 in which the auxiliary heating elements are provided with water inlet and outlet tubes extending horizontally therethrough from front to back and provided with discharge openings along their lengths whereby uniform water circulation is effected.

7. A domestic heater according to claim 4 in which the auxiliary heating elements are provided with water inlet and outlet tubes extending horizontally therethrough from front to back and provided with discharge openings along their lengths whereby uniform water circulation is efiected.

8. A domestic heater according to claim 1 in which the auxiliary heating elements are provided with water inlet and outlet tubes extending horizontally therethrough from front to back and provided with discharge openings along their lengths whereby uniform water circulation is eifected, the water inlet tube being below the water outlet tube and provided with lateral discharge openings and the water outlet tube being provided with openings along its lower surface.

9. A domestic heater according to claim 4 in which the auxiliary heating elements are provided with Water inlet and outlet tubes extending horizontally therethrough from front to back and. provided with discharge openings along their lengths whereby uniform water circulatlon is eirected, the water inlet tube being below the water outlet tube and provided with lateral discharge openings and the water outlet tube being provided with openings along its lower surface.

19. A domestic heater according to claim 4 in which the auxiliary members are of pentagonal cross section, the lower surface being substantially flat, the side surfaces being likewise substantially fiat and at right angles to the bottom surface and the two upper surfaces forming an angle which defines with the bottom of the heating surfaces forming the lowest flue passes flues of substantially triangular cross section.

11. A domestic heater according to claim 4 in

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