Patent Application
20240240827
The present disclosure generally relates to fuel-fired heating appliances, such as furnaces, water heaters, and boilers and, more particularly relates to fuel-fired furnaces having pre-mix fuel systems.
Furnaces, often used to heat households and buildings, generally burn a combustible fuel (for example, natural gas) in a burner thereof to produce hot combustion gasses, which, in turn, provide heat to a heat exchanger thereof before the combustion gasses are exhausted outside the building. Commonly, the hot combustion gasses travel through one or more heat exchanger tubes, and a blower of the furnace forces air across the heat exchanger tubes, thereby transferring heat from the hot combustion gasses to the air. The heated air is then distributed throughout the building via a ductwork. High thermal stresses can occur at interfaces between parts of the furnace, where temperature changes result in non-uniform expansion and contraction between the parts. In some furnaces, heat stresses may occur at an interface between the heat exchanger tubes and a combustion chamber. Typically, a heat exchanger tube is swaged to a central panel that is located proximal to the combustion chamber. Due to heat generated from combustion of the combustible fuel, a swage joint between the heat exchanger tube and the central panel is subjected to high thermal stress. Over a time period, repeated exposure to such high thermal stress will cause metal fatigue of heat exchanger and or joints. This fatigue will cause heat exchanger failure resulting in non-operation or may result in deterioration of efficiency of the furnace.
The detailed description is set forth with reference to the accompanying drawings. In some instances, the use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Throughout this disclosure, depending on the context, singular and plural terminology may be used interchangeably.
The present disclosure relates generally to fuel-fired heating appliance and more particularly to mitigation of thermal stress in the fuel-fired heating appliance. As a result of development of high thermal stress or heat zone at a swage joint located at an interface between heat exchanger tubes and a central plate of the fuel-fired heating appliance, connection between the heat exchanger tubes and a combustion chamber of a burner assembly in the fuel-fired heating appliance may be disturbed, thereby affecting efficiency of the fuel-fired heating appliance.
To address such issues, the present disclosure provides a heat transfer insert that can be disposed at the interface between the heat exchanger tubes and the central plate of the fuel-fired heating appliance. Particularly, the heat transfer insert extends across the interface and allows flow of combustion gas therethrough, where the combustion gas exists the heat transfer insert at a location away from the swage joint, thereby preventing instances of development of heat zone at the swage joint.
In an embodiment, the fuel-fired heating appliance includes a burner and a first housing having an outlet. The first housing is disposed adjacent the burner and configured to receive combustion gas from combustion at the burner. The fuel-fired heating appliance further includes a heat exchanger including a heat exchanger tube having a first bend, a second bend, and an inlet disposed adjacent the outlet of the first housing. The heat exchanger is configured to receive combustion gas from the first housing, where heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger. The fuel-fired heating appliance further includes a blower configured to direct air towards the first bend of the heat exchanger tube. The fuel-fired heating appliance also includes a heat transfer insert disposed at least partially in the heat exchanger tube. The heat transfer insert includes a first end disposed in the first housing and a second end disposed adjacent to the first bend of the heat exchanger tube.
In another embodiment, an ultra-low NOx gas furnace is provided. The ultra-low NOx gas furnace includes a burner and a first housing having an outlet. The first housing is disposed adjacent the burner and configured to receive combustion gas from combustion at the burner. The fuel-fired heating appliance further includes a heat exchanger including a heat exchanger tube having a first bend, a second bend, and an inlet disposed adjacent the outlet of the first housing. The heat exchanger is configured to receive combustion gas from the first housing, where heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger. The fuel-fired heating appliance further includes a blower configured to direct air towards the first bend of the heat exchanger tube. The fuel-fired heating appliance also includes a heat transfer insert disposed at least partially in the heat exchanger tube. The heat transfer insert includes a first end disposed in the first housing and a second end disposed adjacent to the first bend of the heat exchanger tube, where adjacent may be next to, on top of, underneath, aligned with, and so forth.
In another embodiment, a gas furnace is provided. The gas furnace includes a burner and a first housing having an outlet. The first housing is disposed adjacent the burner and configured to receive combustion gas from combustion at the burner. The fuel-fired heating appliance further includes a heat exchanger including a heat exchanger tube having a first bend, a second bend, and an inlet disposed adjacent the outlet of the first housing. The heat exchanger is configured to receive combustion gas from the first housing, where heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger. The fuel-fired heating appliance further includes a blower configured to direct air towards the first bend of the heat exchanger tube. The fuel-fired heating appliance also includes a heat transfer insert disposed at least partially in the heat exchanger tube. The heat transfer insert includes a first end disposed in the first housing and a second end disposed adjacent to the first bend of the heat exchanger tube. Further, the heat transfer insert is positioned such that the combustion gas flows over the heat transfer insert when the combustion gas flows through the outlet of the first housing and the inlet of the heat exchanger.
The second portion 202 houses a blower 218 oriented to direct air towards a rear end of the heat exchanger 208 as shown in
According to an aspect of the present disclosure, the appliance 102 further includes a heat transfer insert 310 having a first end 312 disposed in the first housing 306 and a second end 314 disposed adjacent to the first bend 212 of the heat exchanger tube 210. The heat transfer insert 310 may be formed of various materials, such as a thermally insulating material, a ceramic compound, metals, composite materials, and/or other types of materials. Dimensions may vary depending on the material, for example, metal materials may be thinner than ceramics. Some materials may be ported to allow heat to dissipate from the insert at multiple location or rates as it passes through the heat exchanger tube.
As such, the heat transfer insert 310 is disposed at least partially in the heat exchanger tube 210. The heat transfer insert 310 is embodied as a tubular component configured to extend through the outlet 308 of the first housing 306, inlet 104 of the heat exchanger 208, and through the heat exchanger tube 210. In an embodiment, the heat transfer insert 310 includes a wider diameter section at the first end 312 thereof a comparatively lesser diameter section at the second end 314 thereof. In some embodiments, the first end 312 of the heat transfer insert 310 may be provided as a flange to conceal the outlet 308 of the first housing 306 and create a flow path for the combustion gas. The flow path is defined through the heat transfer insert 310 and along a length thereof. That is, the heat transfer insert 310 is positioned such that the combustion gas flows through the heat transfer insert 310 when the combustion gas flows through the outlet 308 of the first housing 306 and the inlet 104 of the heat exchanger 208. As such, the heat transfer insert 310 extends across an interface between the outlet 308 of the first housing 306 and the inlet 104 of the heat exchanger 208. Therefore, the combustion gas exits the heat transfer insert 310 at a region proximal to the first bend 212 of the heat exchanger tube 210. As described earlier, the blower 218 directs the air towards the first bend 212 of the heat exchanger tube 210. As such, the air flowing across the first bend 212 of the heat exchanger tube 210 absorbs the heat transferred to the heat exchanger tube 210 by the combustion gas exiting the heat transfer insert 310.
In an embodiment, the appliance 102 further includes an interface insert 316 (also shown in
In some embodiments, the heat transfer insert 310 has a material composition that aids sufficient thermal resistance to heat transfer between the combustion gas and the inlet 104 of the heat exchanger 208, as the combustion gas flows through the outlet 308 of the first housing 306, to maintain a stress at the inlet 104 below a yield stress of the inlet 104. In some embodiments, the heat transfer insert 310 may have a wall thickness “T” of about 0.188 inches, such as about 0.2 inches, about 0.25 inches, about 0.15 inches, about 0.5 inches, and so forth.
For the purpose of brevity, the present disclosure illustrates only a cross-section of the first housing 306 and the heat transfer insert 310 coupled to the first housing 306. However, it will be understood that the first housing 306 defines multiple outlets (such as the outlet 308), where each outlet is in fluid communication with one inlet (such as the inlet 104) of the heat exchanger, and the appliance 102 includes multiple heat transfer inserts, where each heat transfer insert extends through one outlet of the first housing 306 and a corresponding inlet 104 of the heat exchanger 208. As such, combustion gas is simultaneously transferred to region proximal to the first bend in each of the heat exchanger tubes.
An experiment was conducted on the appliance 102 to determine an effect of using the heat transfer insert 310. In case of absence of the heat transfer insert 310 in the appliance 102, it was observed that an average temperature of panel 108 was about 986.6° F. and an average temperature at the region proximal to the inlet 104 of the heat exchanger tube 210 was about 1148.6° F. When the heat transfer insert 310 was implemented in the appliance 102, it was observed that the average temperature of panel 108 was 465.8° F. and the average temperature at the region proximal to the inlet 104 of the heat exchanger tube 210 was about 585.2° F. As such, the temperature values, respectively, were reduced by about 50% with the use of the heat transfer insert 310. It was also observed that a percentage of carbon-dioxide in the combustion gas reduced with the use of the heat transfer insert 310 of the present disclosure.
It should be apparent that the foregoing relates only to certain embodiments of the present disclosure and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the disclosure.
Although specific embodiments of the disclosure have been described, numerous other modifications and alternative embodiments are within the scope of the disclosure. For example, any of the functionality described with respect to a particular device or component may be performed by another device or component. Further, while specific device characteristics have been described, embodiments of the disclosure may relate to numerous other device characteristics. Further, although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.
This application claims the benefit of U.S. Application No. 63/439,706, filed Jan. 18, 2023, the entirety of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63439706 | Jan 2023 | US |
