Furnace with heat storage elements

A furnace, for example of the home-heating type, has heat storage elements located in a combustion gas chamber of the furnace, the heat storage elements being placed in a path of flow of combustion gases to increase flow resistance to the combustion gases. The heat storage elements are of such size that they can be inserted into the combustion gas chamber and removed therefrom through door openings normally available in the furnace, for example to change over the furnace from liquid to solid fuels, for cleaning or the like. The storage elements preferably are metal-jacketed bodies of refractory material, for example of clay. If the furnace has a water jacket for heating of water, the clay bodies are placed against the water jacket surface, with the metal jacket of the clay bodies perforated at the side facing the water jacket. A group of such heat storage elements may be commonly supported on a carrier for removal as an assembly.

The present invention relates to a boiler and furnace having a fire box and 
a combustion gas chamber located between the fire box and the flue, and in 
which the boiler-furnace combination is formed with entry openings to 
permit access to the interior thereof. 
It is an object of the present invention to improve the efficiency of heat 
conversion of such boiler-furnace combinations, and more particularly of 
boiler-furnace combinations for use, for example, in home heating. 
SUBJECT MATTER OF THE PRESENT INVENTION 
Briefly, the flow resistance to combustion gases is increased in the 
combustion gas chamber by locating therein heat storage elements. The size 
of the heat storage elements is so selected with respect to the entry 
openings to the boiler-furnace that they can be removed singly, or as an 
assembly mounted on a carrier, and re-introduced thereinto through the 
same opening; in other words, the heat storage elements are not fixedly 
and removably located in the furnace. 
The temperature of the combustion gases exhausted through the flue, and 
then through the smoke stack of the boiler unit is reduced before they 
reach the flue; this improves the overall combustion process and hence 
increases the thermal efficiency of the overall combustion and boiler 
unit. The heat storage elements, introduced into the combustion gas 
chamber thus take up some of the heat which would otherwise be wasted for 
release to water to be heated in the boiler when combustion is terminated. 
The heat storage elements, by virtue of their size related to the openings 
in the boiler-furnace unit, can be removed at any time, for example for 
cleaning or removal of soot, or if the furnace should be changed from oil 
or other liquid fuel to coal or solid fuel, for example. The unit is 
particularly applicable for intermittently fired boiler units, for example 
by an oil burner which is thermostatically controlled and provides, at the 
time of combustion, more heat than can be absorbed by water to be boiled 
in the furnace; this excess heat, otherwise wasted, is stored in the heat 
storage elements to be released to the water to be heated upon termination 
of operation of the burner unit.

The furnace and boiler unit 1 (FIGS. 1, 2) is designed to accommodate, 
selectively, fluid or solid fuels, for example gas, oil or coal. A fire 
box 2, of hollow cylindrical or rectangular shape, is located within the 
boiler space; actual combustion occurs within the fire box 2, particularly 
when the unit is fired with a gaseous or liquid fuel. An oil burner, for 
example, is installed at the end of the fire box 2 in conventional manner; 
the oil burner is not shown. The combustion gases pass, in the direction 
of arrows A, through combustion duct 3 into a combustion gas chamber 4 and 
then pass, again along the arrows, to an exhaust flue connection 24 for 
venting to atmosphere through a smoke stack. 
The boiler has an outer metallic housing 18, an insulating layer 5 
therebeneath, and a water jacket 8 inside the insulating layer 5. The 
water jacket 8 is to be heated by the boiler. The fire box 2 may also be 
surrounded by tubing conducting water, or may be formed of heat transfer 
elements. The boiler-furnace unit is formed with an entry opening 6, 
closed off by a hinged door 6', for example to solid fuel to the boiler, 
such as coal, wood or the like, if it is not desired to operate the 
furnace with liquid or gaseous fuels. An ash pit opening 7, closed off by 
a suitable door 7', is provided at the lower portion of the boiler-furnace 
unit. The two openings 6, 7 are not needed when the unit operates with 
liquid or gaseous fuels. The water jacket 8 surrounds both the fire box 2 
as well as the combination gas chamber 4. 
In accordance with the present invention, heat storage elements 10 are 
located within the combustion gas chamber 4. As shown in FIGS. 1 and 2, 
the heat storage elements partially cover floor 11 of the combustion gas 
chamber; and are located, partially, along the approximately cylindrical 
water jacket 8, at least in portions thereof. By removal of the storage 
elements 10, the unit can be changed over for use with solid fuels at any 
time. A group of the heat storage elements 10 can be combined on a carrier 
14 (FIGS. 1, 2; 7-10) for insertion or removal of a group of such storage 
elements as a unit. The carrier 14 is preferably formed with a handle 30 
for easy handling of the assembly of carrier unit 14 and heat storage 
elements 10. 
Embodiment of FIG. 3: A grate 20 is provided to form a support surface for 
the heat storage elements 10. The combustion gases pass between the 
various heat storage elements 10 in spaces therebetween; otherwise similar 
parts have been given the same reference numerals as in FIGS. 1 and 2, 
incremented by 30. 
Embodiment of FIGS. 4 and 5, in which previously discussed similar elements 
have been given the same reference numerals, incremented by 40: The 
furnace is of well-known construction and formed of individual cast units, 
assembled together. The fire box 42 is in communication with two 
horizontally extending combustion gas chambers 44 closed off by doors 44'. 
The combustion gases then are carried to the flue through exhaust duct 24. 
Inlet and outlet pipes 25, 26 supply and remove the water to be heated. 
The furnace unit has an upper access opening 49 to provide access to an 
intermediate portion of the combustion gas chamber 44. Solid fuel is 
introduced through opening 46, closed off by door 46'. A grate 20 is 
provided to hold the solid fuel, and an ash removal opening is located in 
the outer housing, closed off by door 47. Heat storage elements 10, for 
example assembled on a carrier 14, are introduced horizontally in the 
interior of the combustion gas chambers 44 in the direction of the arrow 
B. 
The heat storage element, individually, is best seen in FIG. 6. A metallic 
jacket 16, formed with holes 12, surrounds a foraminous or stone-like, 
compact mineral mass of high clay content, or other suitable refractory 
material. The heat storage element 10 is essentially rectangular in shape; 
suitable outer dimensions are approximately 15 .times. 6 .times. 4 cm. The 
openings 12 formed in the jacket 16 may extend throughout the jacket; if 
the metal jacket is perforated only through a part of its overall surface 
-- which facilitates cleaning -- then the unit should be so assembled in 
the furnace that the openings 12 are directed to fit against the wall of 
the furnace which is formed by the water jacket. Thus, and referring again 
to FIG. 1, the openings would be located at the outer circumference of the 
units 10 placed on a curved carrier 14 against the interior surface of the 
water jacket 8. 
A group or assembly of storage elements 10 are secured to a common carrier 
14. The common carrier 14 may have various forms, as specifically 
illustrated in FIGS. 7-14. The size of the individual heat storage 
elements 10, or of the entire group or assembly, respectively, is so 
selected that it can be introduced through any one of the openings 6 or 7 
(FIGS. 1, 2); 36, 37 (FIG. 3); 44, 46 (FIGS. 4, 5) by opening the 
respective door after the complete furnace-boiler unit has been assembled 
and, for example, also installed. Preferably, the heat storage elements, 
singly or as a group on the carrier 14, is introduced through the 
respective combustion gas chamber door into the combustion chamber; the 
heat storage elements, singly or as a group, of course can similarly be 
removed for cleaning or change-over of fuel. 
Embodiment of FIGS. 7-9: A carrier 74, of sheet metal, is provided to 
locate a group of heat storage elements 10 thereon. FIG. 10 illustrates a 
carrier which, generally, is similar to that of FIGS. 7 to 9, except that 
the base is curved. 
The separate heat storage unit 10 is secured to the carriers 14, 74, 114, 
respectively, by welding, for example spot-welding at the edges or 
corners. The curvature of carrier 114 (FIG. 10) is selected to fit, at 
least approximately, the inner curved wall of the outer jacket 8 (FIGS. 1, 
2) for introduction of the heat storage elements 10 in a group within the 
exhaust gas chamber 4. The handle 30 is attached to the rear of the 
carrier 14, 74, 114. 
FIG. 11 illustrates a carrier unit 114' for individual heat storage 
elements 10 particularly appropriate for the furnace-boiler unit 
illustrated in FIG. 3. The carrier 114' secures heat elements 10 in 
horizontal as well as in vertical position. The dimensions are so selected 
that the carrier 114', with the individual heat storage elements 10 
secured thereto, can be introduced as a unit through opening 36, or, if 
desired, through opening 37, and can likewise be removed through one of 
the respective openings. 
The heat storage elements can be located on the carrier in various ways. As 
illustrated in FIGS. 12 and 13, the arrangement is so made that carrier 
214 holds a group of heat storage elements in a row, next to each other. 
The heat storage elements 10 are separated from each other by respective 
spaces 217; similar spaces 77 are also shown in FIGS. 7-10, provided and 
located in such a manner that the combustion gases can readily flow around 
the individual heat storge elements 10 to transfer as much heat thereto as 
possible. The structure of FIGS. 12 and 13, particularly adapted for the 
embodiment of the furnace-boiler units of FIGS. 4 and 5, can be introduced 
thereinto by holding the handle 130 and sliding the unit in the direction 
of arrow B; the handle 130 may, additionally, form a support surface for 
the assembly of the units 10. 
If the combustion chamber 4 (FIG. 1) is large, for example in structures of 
the boiler-furnace unit similar to those illustrated in FIGS. 1 and 2, a 
plurality of heat storage elements 10 can be located adjacent each other 
on a single carrier 414, as shown in FIG. 14. The individual heat storage 
elements provide, themselves, structural support for the individual sheet 
metal elements of carrier 414, as clearly apparent from the end view of 
FIG. 14. Various shapes and constructions can be made by building up the 
individual heat storage elements 10 in suitable shapes and forms to fit 
the respective combustion gas chamber, while still maintaining the overall 
dimension such that the unit, when assembled, can be introduced through 
one of the openings always found on such furnace-boiler units. 
The combustion gases will meet an increased flow resistance in the 
combustion gas chamber, as compared with the chamber before the heat 
storage units have been introduced thereto, or as compared with a 
conventional furnace-boiler unit of the prior art. The heat storage units 
10, made of material which cannot burn and which has a high thermal 
capacity, are heated by the hot combustion gases flowing therearound; in 
the gaps between firings of a burner (not shown), for example, between 
operation of an oil burner, heat is released by the heat storage unit to 
the water in the water jacket and to the space surrounding the heat 
storage units. The temperature of the exhaust gases from the unit, with 
the heat storage elements 10 therein, is less than that if the heat 
storage elements are not used, or have been removed. Due to the blockage 
of the free flow of hot exhaust gases, and reduction of the exhaust gases 
escaping through the flue, the overall combustion in the fire box 2, or 
firing space, is improved. It has been found in actual experiments and in 
comparative tests that the ON periods of intermittently operating, 
thermostatically controlled oil burners are less than those in similar 
furnaces which do not have the heat storage elements 10, thus saving 
combustion material and hence energy. The decrease in oil consumption by 
use of additional heat storage elements was substantial. 
Various changes and modifications may be made within the scope of the 
inventive concept.