PRE-MIX FUEL FIRED APPLIANCES HAVING IMPROVED HEAT EXCHANGE INTERFACES

Abstract

Pre-mix fuel fired appliances having improved heat exchange interfaces are disclosed. Embodiments may include a fuel-fired heating appliance having a burner, a first housing comprising an outlet, the first housing disposed adjacent the burner and configured to receive combustion gas from combustion at the burner, and a heat exchanger having a heat exchanger tube with a first bend and a second bend, and an inlet disposed adjacent the outlet of the first housing. The heat exchanger may be configured to receive combustion gas from the first housing. The appliance may include a blower configured to direct air toward the first bend of the heat exchanger tube, and a heat transfer insert disposed at least partially in the heat exchanger tube, the heat transfer insert having a first end disposed in the first housing, and a second end disposed adjacent to the first bend of the heat exchanger tube.

Claims

1. A fuel-fired heating appliance comprising: a burner; a first housing comprising an outlet, the first housing disposed adjacent the burner and configured to receive combustion gas from combustion at the burner; a heat exchanger comprising a heat exchanger tube having a first bend and a second bend, and an inlet disposed adjacent the outlet of the first housing, the heat exchanger configured to receive combustion gas from the first housing, wherein heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger; a blower configured to direct air toward the first bend of the heat exchanger tube; and a heat transfer insert disposed at least partially in the heat exchanger tube, the heat transfer insert comprising a first end disposed in the first housing, and a second end disposed adjacent to the first bend of the heat exchanger tube.

2. The fuel-fired heating appliance of claim 1, wherein 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.

3. The fuel-fired heating appliance of claim 2, further comprising: an interface insert disposed at the outlet of the first housing, and configured to separate the outlet of the first housing from the inlet of the heat exchanger; wherein the heat transfer insert defines a thermal resistance that inhibits heat transfer from the combustion gas to the interface insert.

4. The fuel-fired heating appliance of claim 1, wherein the heat transfer insert extends across an interface between the outlet of the first housing and the inlet of the heat exchanger.

5. The fuel-fired heating appliance of claim 1, wherein the heat exchanger tube has a first linear portion adjacent to the first bend, the first linear portion having a first length; and wherein the heat transfer insert has a second length equal to or greater than the first length.

6. The fuel-fired heating appliance of claim 1, wherein the heat transfer insert has a material composition so that the heat transfer insert provides sufficient thermal resistance to heat transfer between the combustion gas as the combustion gas flows through the outlet of the first housing and the inlet of the heat exchanger to maintain a stress at the inlet below a yield stress of the inlet.

7. The fuel-fired heating appliance of claim 1, wherein the blower does not direct air toward the outlet of the first housing or the second bend of the heat exchanger tube.

8. The fuel-fired heating appliance of claim 1, wherein the heat transfer insert has a length of between 13 inches and 14 inches.

9. The fuel-fired heating appliance of claim 1, wherein the fuel-fired heating appliance is an ultra-low NOx gas furnace.

10. The fuel-fired heating appliance of claim 1, wherein the blower is oriented to direct air toward a rear end of the heat exchanger.

11. An ultra-low NOx gas furnace comprising: a burner; a first housing comprising an outlet, the first housing disposed adjacent the burner and configured to receive combustion gas from combustion at the burner; a heat exchanger comprising a heat exchanger tube having a first bend and a second bend, and an inlet disposed adjacent the outlet of the first housing, the heat exchanger configured to receive combustion gas from the first housing, wherein heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger; a blower configured to direct air toward the first bend of the heat exchanger tube; and a heat transfer insert disposed at least partially in the heat exchanger tube, the heat transfer insert comprising a first end disposed in the first housing, and a second end disposed adjacent to the first bend of the heat exchanger tube.

12. The ultra-low NOx gas furnace of claim 11, wherein 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.

13. The ultra-low NOx gas furnace of claim 12, further comprising: an interface insert disposed at the outlet of the first housing, and configured to separate the outlet of the first housing from the inlet of the heat exchanger; wherein the heat transfer insert defines a thermal resistance that inhibits heat transfer from the combustion gas to the interface insert.

14. The ultra-low NOx gas furnace of claim 11, wherein the heat transfer insert extends across an interface between the outlet of the first housing and the inlet of the heat exchanger.

15. The ultra-low NOx gas furnace of claim 11, wherein the heat exchanger tube has a first linear portion adjacent to the first bend, the first linear portion having a first length; and wherein the heat transfer insert has a second length equal to or greater than the first length.

16. The ultra-low NOx gas furnace of claim 11, wherein the heat transfer insert has a material composition so that the heat transfer insert provides sufficient thermal resistance to heat transfer between the combustion gas as the combustion gas flows through the outlet of the first housing and the inlet of the heat exchanger to maintain a stress at the inlet below a yield stress of the inlet.

17. The fuel-fired heating appliance of claim 11, wherein the blower does not direct air toward the outlet of the first housing or the second bend of the heat exchanger tube.

18. The fuel-fired heating appliance of claim 11, wherein the heat transfer insert has a length of between 13 inches and 14 inches.

19. A gas furnace comprising: a burner; a first housing comprising an outlet, the first housing disposed adjacent the burner and configured to receive combustion gas from combustion at the burner; a heat exchanger comprising a heat exchanger tube having a first bend and a second bend, and an inlet disposed adjacent the outlet of the first housing, the heat exchanger configured to receive combustion gas from the first housing, wherein heat from the combustion gas is conducted through the heat exchanger and transferred to air adjacent to an exterior of the heat exchanger; a blower configured to direct air toward the first bend of the heat exchanger tube; and a heat transfer insert disposed at least partially in the heat exchanger tube, the heat transfer insert comprising a first end disposed in the first housing, and a second end disposed adjacent to the first bend of the heat exchanger tube, wherein 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.

20. The gas furnace of claim 19, further comprising: an interface insert disposed at the outlet of the first housing, and configured to separate the outlet of the first housing from the inlet of the heat exchanger; wherein the heat transfer insert defines a thermal resistance that inhibits heat transfer from the combustion gas to the interface insert.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] 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.

[0005] FIG. 1 illustrates a portion of a fuel-fired heating appliance, in accordance with one or more embodiments of the disclosure.

[0006] FIG. 2 illustrates a cross-section of the fuel-fired heating appliance, in accordance with one or more embodiments of the disclosure.

[0007] FIG. 3A illustrates a burner assembly of the fuel-fired heating appliance of FIG. 2, in accordance with one or more embodiments of the disclosure.

[0008] FIG. 3B illustrates an enlarged portion of a region A in FIG. 2, in accordance with one or more embodiments of the disclosure.

[0009] FIG. 4 illustrates a top view and a sectional side view of a heat transfer insert used in the fuel-fired heating appliance, in accordance with one or more embodiments of the disclosure.

[0010] FIG. 5A illustrates location of heat zone in a conventional fuel-fired heating appliance.

[0011] FIG. 5B illustrates location of heat zone in the fuel-fired heating appliance of the present disclosure.

DETAILED DESCRIPTION

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] FIG. 1 illustrates a first portion 100 of a fuel-fired heating appliance 102 (hereinafter referred to as the appliance 102; see FIG. 2) in accordance with one or more embodiments of the present disclosure. The appliance 102 is alternatively referred to as the gas furnace in the present disclosure. The first portion 100 houses, among other components, a heat exchanger 208 (see FIG. 2) having a heat exchanger tube 210 (see FIG. 2) and an inlet 104 in fluid communication with the heat exchanger tube 210. The first portion 100 also defines an opening 106 configured to fluidly communicate with a draft inducer (not shown) of the appliance 102. The heat exchanger tube 210, at the inlet 104, is attached to a panel 108 of the first portion 100 via a swage joint 110 or other type of joint. Other embodiments may have different configurations and/or may include additional, fewer, or different components. Some components may not be depicted at scale relative to other drawings.

[0018] FIG. 2 illustrates a cross-section of the appliance 102, in accordance with one or more embodiments of the present disclosure. In an embodiment, the appliance 102 is an ultra-low NOx gas furnace. The appliance 102 includes the first portion 100, a second portion 202 located vertically below and adjacent to the first portion 100. The first portion 100 includes a first heat exchanger 204 and a second heat exchanger 206 in fluid communication with the first heat exchanger 204 and downstream of the first heat exchanger 204. As used herein, the term downstream indicates an order in which combustion gas flows through the first heat exchanger 204 and the second heat exchanger 206. In the present disclosure, the first heat exchanger 204 and the second heat exchanger 206 are collectively referred to as the heat exchanger 208 and the heat exchanger tubes of each of the first heat exchanger 204 and the second heat exchanger 206 are collectively referred to as the heat exchanger tube 210. In an aspect, the heat exchanger tube 210 includes a first bend 212 and a second bend 214 located downstream of the first bend 212. In an aspect, the heat exchanger tube 210 has a first linear portion 216 adjacent to the first bend 212, where the first linear portion 216 has a first length L1.

[0019] The second portion 202 houses a blower 218 oriented to direct air towards a rear end of the heat exchanger 208 as shown in FIG. 2. Particularly, the blower 218 is configured to direct air (indicated with elongated arrows) towards the first bend 212 of the heat exchanger tube 210. Owing to such orientation, the blower 218 does not direct the air towards the second bend 214 of the heat exchanger tube 210. Other embodiments may have different configurations and/or may include additional, fewer, or different components. Some components may not be depicted at scale relative to other drawings.

[0020] FIG. 3A illustrates a burner assembly 302 of the appliance, in accordance with one or more embodiments of the present disclosure. FIG. 3A is described in conjunction with FIG. 1 and FIG. 2. The burner assembly 302 is configured to receive combustion air and fuel for combustion in a burner 304 and produce the combustion gas. As used herein, the term combustion air refers to intake air or fresh air used for combustion and the term combustion gas refers to a product of combustion that takes place in the burner 304. The appliance 102 further includes a first housing 306 disposed adjacent the burner 304 and coupled to the burner assembly 302 so as to receive the combustion gas from the burner 304. The first housing 306 defines an outlet 308 that is aligned with the inlet 104 of the heat exchanger 208 to allow flow of the combustion gas from the burner 304 to the heat exchanger tube 210. With reference to FIG. 2, owing to the orientation of the blower 218, it may be observed that the blower 218 does not direct air towards the outlet 308 of the first housing 306. In a conventional furnace, the combustion gas produced in the burner 304 is introduced into the heat exchanger tube 210 at the inlet 104 of the heat exchanger 208. Due to lack of air flowing across the outlet 308 of the first housing 306 or the inlet 104 of the heat exchanger 208, a heat zone is developed at the outlet 308 of the first housing 306. Development of such heat zone affects the swage joint between the inlet 104 of the heat exchanger 208 and the panel 108 of the first portion 100 of the appliance 102. Other embodiments may have different configurations and/or may include additional, fewer, or different components. Some components may not be depicted at scale relative to other drawings.

[0021] FIG. 3B illustrates an enlarged portion of a region A in FIG. 2, in accordance with one or more embodiments of the present disclosure. FIG. 3B is described in conjunction with FIG. 2 and FIG. 3A. The inlet 104 of the heat exchanger 208 is disposed adjacent the outlet 308 of the first housing 306 to establish a fluid communication between the first housing 306 and the heat exchanger 208. As such, the heat exchanger 208 is configured to receive the combustion gas from the first housing 306. As the combustion gas flows through the heat exchanger tube 210, heat associated with the combustion gas is conducted to the heat exchanger tube 210 and transferred to the air flowing across the heat exchanger tube 210 by convection.

[0022] 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.

[0023] 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.

[0024] In an embodiment, the appliance 102 further includes an interface insert 316 (also shown in FIG. 3A) disposed at the outlet 308 of the first housing 306. The interface insert 316 may be embodied as, for example, a plate having predefined thickness and configured to separate the outlet 308 of the first housing 306 from the inlet 104 of the heat exchanger 208. With such arrangement, the heat transfer insert 310 provides a thermal resistance that inhibits or provides resistance of heat transfer from the combustion gas to the interface insert 316.

[0025] FIG. 4 illustrates a top view and a sectional side view of the heat transfer insert 310, in accordance with one or more embodiments of the present disclosure. The heat transfer insert 310 has an outer diameter OD1 at the first end 312 thereof of about 1.689 inches, an outer diameter OD2 at the second end 314 thereof of about 1.179 inches, and an inner diameter ID of about 0.8 inches. Other embodiments may have different dimensions, such as OD1 of between about 1 inch and 2 inches, between about 1.5 inches and 2.5 inches, and so forth, an OD2 of between about 1 inch and 1.5 inches, between about 0.5 inches and 2 inches, and so forth, and an ID of between about 0.5 inches and 1 inch, between about 0.25 inches and about 2 inches, and so forth. In an embodiment, the heat transfer insert 310 has a second length L2 equal to or greater than the first length L1 of the first linear portion 216. In an embodiment, the second length L2 is in a range of about 13 inches to about 14 inches, or about 10 to 15 inches, or about 5 to 20 inches, and so forth.

[0026] 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.

[0027] FIG. 5A and FIG. 5B illustrate top views of a conventional appliance and the appliance 102 of the present disclosure, respectively. Particularly, FIG. 5A and FIG. 5B illustrate the heat zones in the conventional appliance and the appliance 102 of the present disclosure, respectively. As used herein, the conventional appliance either implements a relatively shorter insert or does not include any insert. Due to a short length of the insert or absence of the insert, the combustion gas transfers heat to a region surrounding an inlet of the heat exchanger (such as the inlet 104 of the heat exchanger 208). Since the blower (such as the blower 218) does not direct the air towards the inlet of the heat exchanger, a heat zone develops proximal to the inlet of the heat exchanger, thereby affecting the swage joint between the inlet of the heat exchanger of the center panel (such as the panel 108). On the other hand, the appliance 102 of the present disclosure implements the heat transfer insert 310 that extends between the first housing 306 and the region proximal to the first bend 212 of the heat exchanger tube 210. As such, the combustion gas exits the heat transfer insert 310 at the region proximal to the first bend 212 of the heat exchanger tube 210. As such, the heat zone is shifted to the region proximal to the first bend 212 of the heat exchanger tube 210. Since the blower 218 directs air towards the first bend 212 of the heat exchanger tube 210, the heat transferred by the combustion gas to the heat exchanger tube 210 at the first bend 212 may be absorbed by the air flowing thereacross, thereby preventing heat build-up in the heat exchanger tube 210. Due to the transfer of the heat zone to a region subjected to more airflow and enhanced heat transfer, the swage joint in the appliance 102 of the present disclosure remains unaffected, thereby allowing the appliance 102 to function efficiently. Additionally, owing to the presence of the heat transfer insert 310, requirement of baffles which are configured to direct air towards the heat zone, and which render the appliance 102 complex, may be eliminated. Further, it will be understood that the air directed by the blower 218 first contacts the heat exchanger tubes of the second heat exchanger 206, where the air absorbs some heat before flowing across the heat exchanger tubes of the first heat exchanger 204. As such, instances of cold air being directly routed towards the heat zone is prevented.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.