Heat Reclaimer for Stoves

Abstract

A heat reclaimer mounted on an exhaust-conveying flue, the flue having a flue inside surface in contact with the exhaust, the heat reclaimer including a heat-exchange assembly adjacent to and in contact with the flue. The heat-exchange assembly includes: (a) a fan for moving ambient air; (b) a chamber through which the fan drives the ambient air, the chamber defining a primary airflow direction; and (c) a plurality of heat transfer plates inside the chamber and transverse to the primary airflow direction, the plates defining airflow openings therethrough and having at least an edge in solid-to-solid thermal contact with a flue inside surface portion inside the chamber, thereby heating the ambient air with heat from the exhaust.

Description

FIELD OF THE INVENTION

The present invention relates to heating systems for homes and the like, and more particularly to a heat exchanger for reclaiming heat which is lost the exhaust from the combustion of wood, pellets, coal, gas and the like in equipment such as but not limited to a free-standing stove.

BACKGROUND OF THE INVENTION

A number of buildings such as homes and small businesses are at least partially heated using heating apparatus such as a free-standing stove having a flue through which the exhaust from the combustion of fuels (e.g., wood, pellets, coal and gas) in the heating apparatus. As is well-known, such exhaust streams contain a significant amount of heat which, if some of it can be recovered (reclaimed), increases the overall efficiency of the heating apparatus.

A number of heat reclaiming devices are known in the prior art. For example, a product called Magic Heat is available from HY-C® Company of St. Louis, Mo. The Magic Heat product utilizes heat recovery tubes which are placed inside and across the flue such that the hot exhaust gases flow around the outside of the heat recovery tubes. A fan blows room air through the heat recovery tubes back into the room.

Another product called Miracle Heat® is available from United States Stove Company of South Pittsburgh, Tenn. The Miracle Heat product is disclosed in U.S. Pat. No. 4,552,772. Like the Magic Heat product, the Miracle Heat product has heat recovery tubes inside and across the exhaust flue and a fan to drive room air therethrough. However, the fan is configured to also drive some of the room air around the outside of a portion of the flue which is within the housing of the Miracle Heat product.

There are at least two important problems with the heat reclaiming devices of the prior art, namely (1) the difficulty of cleaning the creosote, tars and other combustion products which have been deposited on the inside of the flue and (2) the complexity of the manufacture of the devices. Cleaning of the flue must be done periodically for safety—to prevent chimney fires, and the complexity of manufacture results in higher up-front cost. Both of these issues are addressed by the present invention.

OBJECTS OF THE INVENTION

It is an object the inventive heat reclaimer disclosed herein to provide a device which safely transfers heat usually lost up the flue of a stove to the space in which the stove is located.

Another object of the present invention is to provide a heat reclaimer which retains the free opening of the flue such that the flue can be easily cleaned with standard chimney- or flue-cleaning tools.

Another object of the present invention is to provide a heat reclaimer which is cost effective to manufacture.

Yet another object of the present invention is to provide a heat reclaimer which provides efficient heat transfer to the space in which the flue is located.

These and other objects of the invention will be apparent from the following descriptions and from the drawings.

SUMMARY OF THE INVENTION

The present invention is a heat reclaimer mounted on an exhaust-conveying flue having a flue inside surface in contact with the exhaust. The heat reclaimer includes a heat-exchange assembly which is adjacent to and in contact with the flue. The heat-exchange assembly includes: (a) a fan for moving ambient air; (b) a chamber through which the fan drives the ambient air, the chamber defining a primary airflow direction; and (c) a plurality of heat transfer plates inside the chamber and transverse to the primary airflow direction, the plates defining airflow openings therethrough and having at least an edge in thermal contact with the flue inside surface portion inside the chamber, thereby heating the ambient air with heat from the exhaust.

In highly-preferred embodiments of the inventive heat reclaimer, the plates are configured as pairs of plates in U-shaped form having a base in thermal contact with the flue inside surface portion and the pair of plates extending from the base. In some of these embodiments, the pairs of plates are parallel to one another, and further, in some embodiments, the airflow openings in one plate of each pair are aligned with the corresponding openings in the other plate of the pair.

Other embodiments of the inventive heat reclaimer may include or more of the following features: the plates being parallel to one another; the airflow openings on a plate defining a pattern thereon and each plate having the same pattern of openings; the airflow openings in a plate being aligned with the corresponding openings in one of its immediately-adjacent plate; and the plates being substantially perpendicular to the primary airflow direction; and the flue having an outside surface and one edge of each plate has direct solid-to-solid thermal contact with the outside surface of the flue.

The term “ambient air” as used herein refers to the air outside of the exhaust flue in the space in which the flue is located and which passes through the inside of the heat-transfer assembly chamber.

The term “primary airflow direction” as used herein refers to the general direction of airflow through a chamber. Airflow through the chamber of the heat-exchange assembly of the present invention is likely to be at least partially turbulent flow and which is flowing both through and around the plates which are transverse to (i.e., across) the primary flow through the chamber. The “primary airflow direction” is therefore simply aligned with the major axis of the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective-view drawing of the heat reclaimer of this invention, shown mounted in a section of a flue of a free-standing stove.

FIG. 2A is an exploded-view perspective drawing of the heat reclaimer of FIG. 1.

FIG. 2B is a second exploded-view perspective drawing of the heat reclaimer of FIG. 1 as viewed from a different angle from that of FIG. 2A.

FIG. 3 is a perspective-view drawing of the heat-exchange assembly of the heat reclaimer of FIG. 1 but shown without the fan.

FIG. 4A is a perspective-view drawing of a one embodiment of the internal components of the inventive heat reclaimer.

FIGS. 4B-4D are together a three-view set of top, front and side views of the embodiment of FIG. 4A.

FIG. 5A is a perspective-view drawing of a second embodiment of the internal components of the inventive heat reclaimer.

FIGS. 5B-5D are together a three-view set of top, front and side views of the embodiment of FIG. 5A.

FIG. 6A is a perspective-view drawing of a third embodiment of the internal components of the inventive heat reclaimer.

FIGS. 6B-6D are together a three-view set of top, front and side views of the embodiment of FIG. 6A.

FIG. 7A is a perspective view of one embodiment of a folded pair of heat transfer plates. FIG. 7B is a drawing of the unfolded pair of heat transfer plates of FIG. 7A.

FIG. 8A is a perspective view of a second embodiment of a folded pair of heat transfer plates. FIG. 8B is a drawing of the unfolded pair of heat transfer plates of FIG. 8A.

FIG. 9A is a perspective view of a third embodiment of a folded pair of heat transfer plates. FIG. 9B is a drawing of the unfolded pair of heat transfer plates of FIG. 9A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Several embodiments or configurations of various components of the inventive heat reclaimer disclosed herein are shown, but like reference numbers are used for such different configurations without ambiguity. Note that not all components are numbered in each drawing. A table of reference numbers is included below for convenience.

COMPONENT                        REF #
heat reclaimer                   10
flue                             12
flue cover section of heat reclaimer 12′
flue inside surface              14
flue inside surface portion      14p
heat-exchange assembly           16
fan                              18
chamber                          20
primary airflow direction        22
heat transfer plate              24
airflow opening                  26
plate edge                       28
heat transfer plate pair         30
plate pair base                  30b
plate pair unfolded              30u
plate opening pattern            32
ambient air outlet               34
heat outlet assembly             34a
heat outlet opening              34o
ambient air inlet                36
assembly internals (first embodiment) 40-1
assembly internals (second embodiment) 40-2
assembly internals (third embodiment) 40-3
stove                            42
fan cover                        44
chamber cover                    46

FIG. 1 is a perspective-view drawing of one embodiment 10 of the inventive heat reclaimer (also 10) of this invention, shown mounted in a section of a flue 12 of a free-standing stove 42. FIGS. 2A and 2B are two exploded-view perspective drawings of heat reclaimer 10 which illustrate the various components of heat reclaimer 10. Heat reclaimer 10 is installed integrally with flue 12 such that portions of flue 12 may be considered to be both part of flue 12 and well as part of heat reclaimer 10. A flue cover section 12′ is such a component. Heat reclaimer 10 includes a flue inside surface 14 which receives heat transferred from exhaust from stove 42. On the opposite side of flue inside surface 14 is a flue inside surface portion 14p (see also FIGS. 4A, 4B, 5A, 5B, 6A and 6B) inside of a chamber 20. Heat is transferred to the inside components of chamber 20 and into the airflow flowing therethrough via flue inside surface portion 14p.

FIGS. 2A and 2B are two exploded-view perspective drawings of heat reclaimer 10 which illustrate the various components of heat reclaimer 10. Referring primarily to FIGS. 2A and 2B, heat reclaimer 10 includes a heat-exchange assembly 16 and a fan 18 for moving ambient air (e.g., room air) (i) through an ambient air inlet 36, (ii) through a chamber 20, and (iii) back into the room through an ambient air outlet 34. Heat-exchange assembly 16 also includes a plurality of heat transfer plates 24, each including at least one airflow opening 26.

FIG. 3 is a perspective-view drawing of heat-exchange assembly 16 of FIG. 1 without fan 18, illustrating the relative configuration of many of the components and features of heat reclaimer 10.′

The heat transfer plates of embodiment 10 are configured as pairs 30 of plates 24 in U-shaped form having a plate pair base 30b between plates 24 of pair 30. These details are more easily seen in FIGS. 7A through 9B. These figures include three pairs of drawings which illustrate three embodiments of heat transfer plate pairs 30. Each of the three embodiments is illustrated with a perspective drawing of pair 30 of plates 24 and a corresponding drawing of an unfolded pair 30u. Each of the three embodiments has a different plate opening pattern 32. The three embodiments of FIGS. 7A through 9B are not intended to be limiting. Note that each plate 24 of the embodiment of FIGS. 9A and 9B includes a single airflow opening 26 with a complex shape.

Note also that airflow openings 26 of plates 24 of each pair 30 are aligned with the corresponding openings 26 of the other plate 24 in pair 30. Such a configurational feature is not intended to be limiting.

Three sets of four figures, FIGS. 4A-4D, FIGS. 5A-5D and FIGS. 6A-6D, illustrate three different embodiments 40-1, 40-2 and 40-3, respectively, of internal assembly components of heat reclaimer 10. The three sets of figures include similar views with one exception—embodiment 40-1 of FIGS. 4A-4D include a flue cover section 12′ of heat-exchange assembly 16 while the other two sets of figures do not include such component.

Referring particularly now to the three embodiments 40-1, 40-2 and 40-3 of FIGS. 4A-4D, FIGS. 5A-5D and FIGS. 6A-6D, each heat transfer plate 24 has a plate edge 28 which is in solid-to-solid thermal contact with flue inside surface portion 14p, plate edges 28 each being part of a pair base 30b. The three different embodiments 40-1, 40-2 and 40-3 all include a plurality of plate pairs 30 but which are aligned differently. In embodiment 40-1, all of plates 24 are parallel to each other and perpendicular of the primary airflow direction 22 (see FIG. 2B) as defined above. As such, plates 24 are all transverse to primary airflow direction 22. In embodiment 40-2, some plate pairs 30 are oriented at an angle with respect to other pairs 30 which are perpendicular to primary airflow direction 22. As in embodiment 40-1, plates 24 are all transverse to primary airflow direction 22 in embodiment 40-2. In embodiment 40-3, some of the plate pairs 30 are oriented parallel to primary airflow direction 22 and are therefore not transverse to primary airflow direction 22. Since primary airflow direction 22 is defined above as a general direction and since local airflow turbulence may result in varying flow directions, such plate 24 orientation may still be beneficial for heat transfer.

Referring again to FIGS. 2A and 2B, heat reclaimer 10 includes a fan cover 44 and a chamber cover 46. Chamber cover 46 encloses chamber 20 along with flue inside surface portion 14p. In addition, heat reclaimer 10 includes a heat outlet assembly 34a which has a plurality of heat outlet openings 34o.

The overall concept of this invention is to transfer heat from the exhaust of a combustion source such as a wood-burning stove while maintaining relatively unobstructed flow within the flue such that periodic cleaning of the flue is relatively simple. To accomplish this, ambient airflow is provided through a chamber which contains a significant amount of heat transfer area in the configuration of the components within the chamber through which “clean” ambient air flows.

While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.

Claims

1. A heat reclaimer mounted on an exhaust-conveying flue, the flue having a flue inside surface in contact with the exhaust, the heat reclaimer including a heat-exchange assembly adjacent to and in contact with the flue, the heat-exchange assembly including: a fan for moving ambient air;a chamber through which the fan drives the ambient air, the chamber defining a primary airflow direction; anda plurality of heat transfer plates inside the chamber and transverse to the primary airflow direction, the plates defining airflow openings therethrough and having at least an edge in solid-to-solid thermal contact with a flue inside surface portion inside the chamber,

2. The heat reclaimer of claim 1 wherein the plates are configured as pairs of plates in U-shaped form having a base in thermal contact with the flue inside surface portion and the pair of plates extending from the base.

3. The heat reclaimer of claim 2 wherein the pairs of plates are parallel to one another.

4. The heat reclaimer of claim 3 wherein the airflow openings in one plate of each pair are aligned with the corresponding openings in the other plate of the pair.

5. The heat reclaimer of claim 1 wherein the plates are parallel to one another.

6. The heat reclaimer of claim 1 wherein the airflow openings on a plate define a pattern thereon and each plate has the same pattern of openings.

7. The heat reclaimer of claim 1 wherein the airflow openings in a plate are aligned with the corresponding openings in one of its immediately-adjacent plate.

8. The heat reclaimer of claim 1 wherein the plates are substantially perpendicular to the primary airflow direction.