Chimney Systems with Integrated Waste Heat Recovery and Related Methods

This utility patent application is based on and claims priority to U.S. Provisional Application 63/574,323, filed on 4 Apr. 2024, which is incorporated by reference herein in its entirety.

The disclosure generally relates to heat recovery during the venting of combustion products.

Chimneys, stacks, or vents are conduits used in high-temperature applications, such as for venting products of combustion from boilers and other heating appliances. Depending upon the application, these conduits can be designed as single, double, or triple wall, for example, with or without insulation to reduce the surface or skin temperature of the conduit. Conventionally, the purpose of these systems is to safely convey warm/hot exhaust away from the heating appliances and to the outside. Thus, these systems are not designed to capture or retain the heat in the exhaust.

In this regard, chimney systems with integrated waste heat recovery and related methods are provided. An example embodiment of chimney system is configured for use with a heating appliance located within a structure. The heating appliance has a combustion air inlet and an exhaust air outlet. The system comprises: an inner stack pneumatically communicating with the exhaust air outlet and extending in length to an exhaust, disposed exterior to the structure, the inner stack defining a flow path to direct exhaust gasses from the exhaust air outlet to the exhaust; an outer stack extending along a portion of the length of the inner stack between an intake end and an appliance end, the outer stack being disposed about an exterior of the inner stack and being spaced therefrom to form a combustion air passage therebetween, the combustion air passage being annular in cross-section and in a heat transfer relationship with the exterior of the inner stack; a combustion air opening disposed at the intake end of the outer stack, the combustion air opening being configured to receive combustion air and provide the combustion air to the combustion air passage; an air dam disposed at the appliance end of the outer stack to terminate the combustion air passage; and a combustion air conduit pneumatically communicating with the combustion air passage at the appliance end of the outer stack and upstream of the air dam, the combustion air conduit being configured to direct the combustion air from the combustion air passage to the combustion air inlet of the heating appliance; wherein, in operation, heat is transferred from the exhaust gasses being directed from the heating appliance to the combustion air directed through the combustion air passage.

An example embodiment of a method for integrated waste heat recovery is configured for use with a heating appliance located within a structure. The heating appliance has a combustion air inlet and an exhaust air outlet. The method comprises: providing an inner flow path to direct exhaust gasses from the exhaust air outlet of the heating appliance to an exhaust, which is disposed exterior to the structure; providing a combustion air passage annular in cross section and disposed about an exterior of the inner flow path, the combustion air passage being in a heat transfer relationship with the inner flow path; providing a combustion air flow path to direct the combustion air from the combustion air passage to the combustion air inlet of the heating appliance; and transferring heat from the exhaust gasses of the heating appliance being directed along the inner flow path to the combustion air being directed in a counter-flow direction through the combustion air passage.

Other objects, features, and/or advantages may become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

The following describes several embodiments of chimney systems with integrated waste heat recovery and related methods. It is to be understood that the invention is not limited in its application to the details of the arrangements shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.

Reference throughout this specification to “one embodiment”, “an embodiment”, “one example”, and/or “an example” (or language similar thereto) means that a particular feature, structure, and/or characteristic described in connection with the embodiment or example is included in at least one embodiment or version. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, “one example”, and/or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the feature(s), structure(s), and/or characteristic(s) may be combined in any suitable combination(s) and/or sub-combination(s) in one or more embodiments or examples.

In this regard,depict an example embodiment of a chimney system with integrated waste heat recovery (hereinafter “chimney system”). Chimney systemis configured for use with a heating appliance(such as a boiler, for example), that is typically located within a structure(for example, a building). Heating applianceincorporates a combustion air inletand an exhaust air outlet. Chimney systeminterconnects with heating applianceand is configured to direct a flow of combustion air to combustion air inletand direct exhaust gasses from exhaust air outlet.

Chimney systemincludes an inner stackand an outer stack. Each stack may be formed of multiple sections (see, for example, sectionsandof) that are joined in a generally end-to-end configuration to form a flow path. The sections can be assembled with a male/female joint system with or without flanges that can be secured with an optional locking band (e.g.,of). The joint between adjacent sections can be sealed with gasket material (e.g., a graphite gasket) configured to withstand high temperature and pressure.

Inner stack(see,) pneumatically communicates with exhaust air outlet. Inner stackdefines a flow paththat extends from exhaust air outletto exhaust. Inner stackis operative to direct exhaust gasses from exhaust air outletoutward and through exhaust. Typically, exhaustis disposed outside of the structure in which heating applianceis located.

An outer stackextends from an intake endto an appliance endalong a portion of the length of inner stack. Outer stackalso is disposed about an exterior of inner stackand is spaced from inner stackto form a combustion air passagetherebetween. Combustion air passageis annular in cross-section and is disposed in a heat transfer relationship with the exteriorof inner stack.

As best shown in, an intake conedefining a combustion air openingis disposed at intake end. Intake coneis configured to allow for smooth transition of ambient air into the annulus of combustion air passage. Combustion air openingis annular in cross section and is positioned about inner stack. Oftentimes, combustion air openingis located within the structure in which heating applianceis located. Combustion air openingis configured to receive combustion airand provide the combustion air to combustion air passagefor routing the combustion air toward heating appliance, i.e., in a counter-flow direction relative to the flow direction of the exhaust gasses. As shown in, combustion air passageexhibits an annular cross section.

At appliance endof outer stack, an air damis disposed for terminating combustion air passage. As shown in, air damis annular and is positioned between an inner surfaceof outer stackand an outer surfaceof inner stack. Notably, air dampneumatically seals this end of combustion air passageupstream of combustion air inletof heating appliance.

Upstream of air dam, a combustion air conduitis disposed to direct combustion airfrom combustion air passageto combustion air inletof heating appliance. Specifically, an inletof combustion air conduitpneumatically communicates with combustion air passage. In the depicted embodiment, outer stackincorporates a first aperturedefining a first opening. Inletof combustion air conduitcommunicates with combustion air passagevia first openingand reconfigures the flow of combustion air into a non-annual flow.

A mechanical exhaust fan(see,, for example) may be included to provide mechanically induced draft for drawing out exhaust gasses, such as when a heat source of the heating appliance does not produce sufficient draft for proper operation. Although depicted inas being disposed at the exhaust(i.e., the vent termination point), in other embodiments, mechanical exhaust fanmay be disposed inline between heating applianceand the vent termination point.

In some embodiments, a mechanical intake fan(see,, for example) may be included to provide mechanically induced draft for enhancing air flow into combustion air openingand through combustion air passage. The combustion air flow could also be created by another means such as a heating appliance with a power burner (not shown). As would be understood by one of skill in the art, a fan system for the exhaust and/or intake air may incorporate other components (e.g., draft controllers) to maintain the proper air flow as the application dictates. These controllers should maintain draft via pressure transducers measuring the pressure in the exhaust and intake air streams.

In operation, as relatively hot exhaust gasses are directed along flow pathdefined by inner stack, heat is transferred from the exhaust gasses to combustion airthat is being directed through combustion air passagetoward heating appliance. Specifically, by creating flows in opposite directions separated by the inner stack, the heat of the hotter exhaust gasses is transferred by convection onto the inner surface of the inner stack and then conducted to the outer surface where it heats the cooler unconditioned air flowing through the annulus of the combustion air passage.

The heat transfer between the two flows can be enhanced in several ways. For instance, the outer stack can be insulated with insulation material to limit the convective heat loss from the outer stack to the surrounding environment. As another example, a turbulator assembly may be used to create turbulence in the exhaust air flow, which may lead to more heat being transferred between the two flows. Additionally, or alternatively, the inner stack may be fitted with fins that protrude inwardly from the inner surface to create turbulence and increase the heat transfer surface area.

The described concepts can be used in conjunction with heating appliances and high-temperature exhaust applications. Of note, by preheating the combustion air through the heat exchange, combustion efficiency of the associated heating appliance may be substantially increased. Additionally, removal of heat from the exhaust gasses may reduce the appearance of exhaust plumes.

As mentioned, one or more turbulator assemblies may optionally be disposed along flow pathto disrupt the flow of exhaust gasses and enhance heat transfer. In the example embodiment of, two turbulator assemblies (,) are provided that are spaced from each other; however, for ease of description, only one will be described in detail. It should be noted that placement of one or more turbulators along a flow path may deviate from the positions shown.

With reference to, turbulator assemblyis modular in configuration and includes an inner stack section, an outer stack section, and a turbulator section. Inner stack section, in addition to defining a portion of flow path, incorporates an inner stack aperturethat defines an inner stack opening. Inner stack sectionalso exhibits a centerline. Outer stack sectionincorporates an outer stack aperturethat defines an outer stack opening.

As shown in, turbulator sectionincludes an inner stack panelthat is configured to seal inner stack opening, such as with an interposed gasket. Inner stack panelalso mounts a flow disruption assemblythat is configured to alter the flow of exhaust gasses along flow pathto disrupt the temperature gradient, thereby increasing heat transfer to air within the combustion air passage.

Flow disruption assemblyincludes one or more fins (e.g., finsand) mounted to an axial shaftvia one or more arms (e.g., arm). The fins extend outwardly from axial shaftand radially across flow path, although various other arrangements may be used. In this embodiment, each fin is generally planar and is fixed in an inclined position with respect to flow pathto divert gasses outwardly from centerline. In embodiments in which multiple fins are used, sets (e.g., pairs) of fins may be mounted at various positions along and/or about the flow path. For instance, one or more fins may be positioned downstream of one or more other fins.

Attachment of flow disruption assemblyto inner stack panelfacilitates removal of turbulator sectionfrom turbulator assembly. In this regard, an optionally hinged outer door, which may be secured to outer stackvia adjustable latches (e.g., latch), provides selective access to outer stack openingof outer stack sectionto permit installation and removal of turbulator section, such as may be performed for cleaning of flow disruption assembly. A gasketmay be interposed between outer doorand outer stack section.

A perceived benefit of the removable turbulator section is to provide easy access for cleaning in applications where the exhaust air can contaminate and clog other designs. Note also that removal of turbulator sectionmay be a toolless operation, such as in embodiments that use wing nuts (e.g., nut) for securement of inner stack panel.

An example embodiment of a method for integrated waste heat recovery of a heating appliance is shown in. As shown in, methodmay be construed as beginning at block, in which an inner flow path is provided to direct exhaust gasses from an exhaust air outlet of the heating appliance to an exhaust. In some embodiments, the exhaust is disposed exterior to the structure in which the heating appliance is located. In block, a combustion air passage, annular in cross section, is disposed about an exterior of the inner flow path, with the combustion air passage being in a heat transfer relationship with the inner flow path. In block, a combustion air flow path is provided to direct the combustion air from the combustion air passage to the combustion air inlet of the heating appliance. Then, as shown in block, heat from the exhaust gasses is transferred to the combustion air that is being directed in a counter-flow direction through the combustion air passage.

In some embodiments, such a method may additionally include disrupting the flow of the exhaust gasses along the inner flow path to enhance heat exchange. As described previously, for example, disrupting the flow of the exhaust gasses may be provided by a flow disruption assembly that is removably positioned along the inner flow path. If so equipped, a related method may further include removing the flow disruption assembly from the inner flow path, cleaning the flow disruption assembly (to remove any accumulation/debris that may degrade performance), and reinstalling the flow disruption assembly.

The embodiments described above are illustrative of the invention and it will be appreciated that various permutations of these embodiments may be implemented consistent with the scope and spirit of the invention as defined by the claims. By way of example, although described as being used primarily for combustion air heating, various other uses, such as heating of the ambient air and/or sending the heated air to a secondary heat exchanger, may be provided. Any examples provided are non-limiting examples.