RELATED APPLICATIONS

[0001 ] This application claims the benefit of U.S . Provisional Appln. No. 62/472,842, filed March 17, 2017, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates generally to burner systems and, more specifically, relates to a heat exchanger for a burner.

BACKGROUND

[0003] Requirements for NO _x emissions continue to become more stringent. California's

South Coast Air Quality Management District is the world leader in NOx regulations. Recently enacted legislation for forced air furnaces have caused a shift in the type of combustion required for these products. Inshot burners, which have been the industry standard for many years are not capable of meeting the new NO _x requirements. Inshots are relatively low primary aeration burners, which typically fired into a tubular type heat exchanger. Secondary air is introduced around the perimeter of the centrally located flame. The secondary air gradually enters the flame to complete the combustion as it makes its way down the length of the tube. The secondary air also shields the tube inlet from exposure to the flame as it enters the tube.

[0004] The relatively low primary air flame also has a lower flame temperature than a more highly aerated premixed flame. Since most furnace manufacturers make high volumes of furnaces for sale throughout the country, it is not practical or cost effective to make a completely new furnace model for the California market. The desire of these manufactures is to use as much of the existing furnace as possible, with only the burner changing to meet the requirements. The best option for meeting the requirements is to switch to a fully premixed burner system. This system, however, can cause overheating of the vestibule panel and heat exchanger tubes. SUMMARY

[0005] In one example, a heat exchanger for an appliance having a burner includes at least one tubular heat exchanger section extending from an inlet end aligned with the burner and an outlet end. The inlet end includes a first portion having a first inner diameter and a second portion having a second inner diameter greater than the first diameter.

[0006] In another example, a furnace includes a burner including a distributor having at least one curved second portion for providing a flame. A vestibule panel connected to the burner includes an opening aligned with each second portion downstream of the burner. A heat exchanger has at least one tubular heat exchanger section extending from an inlet end aligned with each second portion of the burner and an outlet end. The inlet end includes a first portion having a first inner diameter and a second portion having a second inner diameter greater than the first diameter.

[0007] In yet another example, a heat exchanger for an appliance having a burner includes a plurality of heat exchanger sections each extending from an inlet end aligned with the burner and an outlet end. The inlet and outlet ends are positioned on the same side of the heat exchanger section. Each inlet end includes a first portion having a first inner diameter and a second portion having a second inner diameter greater than the first diameter A ceramic insulation sleeve is positioned within the second portion of each heat exchanger section and has an inner diameter substantially equal to the first diameter of the inlet end. The insulation sleeve helps to protect the inlet end from thermal damage.

[0008] Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is schematic illustration of an appliance including a heat exchanger in accordance with the present invention.

[0010] Fig. 2A is an assembly view of components including the heat exchanger in the appliance of Fig. 1.

[0011 ] Fig. 2B is an exploded view of alternative components of the appliance. [0012] Fig. 3 is a side view of a heat exchanger section of the heat exchanger in Fig. 2A.

[0013] Fig. 4 is a section view of Fig. 3 taken along line 4-4.

[0014] Fig. 5 is a front view of a vestibule panel of the appliance of Fig. 1 A.

[0015] Fig. 6 is a section view of Fig. 5 taken along line 6-6.

[0016] Fig. 7A is a front view of an insulation sleeve for the heat exchanger section of Fig. 3.

[0017] Fig. 7B is an enlarged view of a portion of the heat exchanger section of Fig. 3 including the insulation sleeve of Fig. 7A.

[0018] Fig. 8 is a schematic illustration of operation of the heat exchanger in a first example.

[0019] Fig. 9 is a schematic illustration of operation of the heat exchanger in a second example.

DETAILED DESCRIPTION

[0020] The present invention relates generally to burner systems and, more specifically, relates to a heat exchanger for a burner. Referring to Fig. 1, the heat exchanger is provided in an appliance, such as a furnace 10. In one example, the furnace 10 includes a heat exchanger 20, vestibule panel 40, burner 50, gasket 60, and an inducer blower 68 (Fig. 2A). Alternatively, the furnace 10 can include the heat exchanger 20, vestibule panel 40a, burner 50, gasket 60, and a secondary heat exchanger 80 (see Fig. 2B). The burner 50 can be positioned nearer the bottom of the vestibule panel 40 (Fig. 2A) or nearer the top of the vestibule panel 40a (Fig. 2B) depending on the configuration of the appliance 10. The remainder of the description is directed to the appliance 10 component configuration of Fig. 2A unless otherwise noted.

[0021 ] As shown in Figs. 3-4, the heat exchanger 20 includes at least one heat exchanger section 22. Although five sections 22 are shown it will be appreciated that more or fewer sections - including a single section - can be provided. The sections 22 are hollow and substantially identical to one another.

[0022] Each heat exchanger section 22 is formed as a serpentine tube extending along a centerline 23 from a first or inlet end 24 to a second or outlet end 26. The inlet end 24 terminates at an opening 25 and the outlet end 26 terminates at an opening 27. As shown, the ends 24, 26 and therefore the openings 25, 27 are positioned on the same [left] side of the heat exchanger section 22. Alternatively, the ends 25, 26 and openings 25, 27 could be positioned on opposite sides of the heat exchange section 22 (Fig. 2B). In any case, a passage 30 extends the entire length of the section 22 from the opening 25 to the opening 27.

[0023] The inlet end 24 of each heat exchanger section 22 includes a wall 70 defining a first portion 74 and a second portion 76 upstream of the first portion. The first portion 74 has a first inner diameter Φι and the second portion 76 has a second inner diameter Φ ₂ greater than the first inner diameter. A tapered or angled neck 78 connects the first and second portions 74, 76 together. The heat exchanger section 22 can have substantially the same first inner diameter Φι from the neck 78 to the opening 27 in the outlet end 26. Alternatively, the first inner diameter Φι can taper down in a direction extending towards the opening 27 in the outlet end 26 (not shown).

[0024] Referring to Figs. 5-6, the vestibule panel 40 can be planar and includes opposing sides 42, 44. A layer of thermal insulation (not shown) can line at least a portion of the side 44. First openings 43 and second openings 45 extend entirely through the vestibule panel 40 between the sides 42, 44. The number of first openings 43 and second openings 45 each corresponds with the number of heat exchanger sections 22. The first openings 43 are positioned nearer the bottom of the vestibule panel 40. The second openings 45 are positioned nearer the top of the vestibule panel 40. The first openings 43 could, however, be located nearer the top of the vestibule panel 40a (see Fig. 2B).

[0025] The sections 22 are connected to the vestibule panel 40 via a swaged or welded connection 46 (Fig. 2A). The inlet ends 24 of the sections 22 are positioned in the openings 43 in the vestibule panel 40. This aligns the openings 25 in the inlet ends 24 with the openings 43 in the vestibule panel 40. The outlet ends 26 are positioned in the openings 45 in the vestibule panel 40 and connected thereto by swaging or welding at 46. This aligns the openings 27 in the outlet ends 26 with the openings 45 in the vestibule panel 40. The fluid passage 30 of each section 22 is therefore fluidly connected with a corresponding pair of openings 43, 45 in the vestibule panel 40.

[0026] As shown in Figs. 2A-2B, the burner 50 is positioned upstream of the vestibule panel 40 and the sections 22, i.e., secured to the side 42 of the vestibule panel. The burner 50 can constitute a non-premixed burner or a pre-mixed burner. The premixed burner can be partially or fully premixed. In one example, the burner 50 is a fully premixed, low NO _x burner. The burner 50 includes a housing 52 defining a combustion chamber 54 therein. A distributor 56 is secured to the housing 52 to close the combustion chamber 54.

[0027] The distributor 56 is formed from a thin, durable, and heat-resistant material such as metal, a metal screen or expanded metal. The distributor 56 includes a planar first portion 57 and at least one dimple or second portion 58 formed or provided on the first portion. In one example, each second portion 58 is curved or dimple-shaped, e.g., rounded, hemispherical, concave or convex. Every second portion 58 may have the same configuration or different configurations from one another. A concave second portion 58 provides a narrow, long or elongated flame while a convex second portion will provide a wider, more dispersed flame.

[0028] The number, size, and spacing of the second portions 58 coincides with the number, size, and spacing of the downstream first openings 43 and heat exchanger sections 22 present. In particular, each second portion 58 is aligned with the inlet end 24 of an associated heat exchanger section 22 such that the end of each section is in fluid communication with each second portion. Each second portion 58 can be configured to provide a desired flame

characteristic or profile from the burner 50 to the respective heat exchanger section 22.

[0029] The gasket 60 is positioned between the distributor 56 -more specifically the entire burner 50 - and the side 42 of the vestibule panel 40. The gasket 60 includes a plurality of openings 62. Each opening 62 is aligned with one of the second portions 58 on the distributor 56 and one of the first openings 43 in the vestibule panel 40. The openings 62 are also each aligned with one of the inlet ends 24 - more specifically the openings 25 therein - of the sections 22 on the opposite side 44 of the vestibule panel 40.

[0030] Referring to Figs. 7A-7B, an optional insulation sleeve 90 can be inserted into the first end 24 of each heat exchanger section 22. The insulation sleeve 90 is tubular and includes a passage 91 extending between a pair of openings 92, 94. The insulation sleeve 90 has an inner diameter Φ ₃ substantially equal to the first diameter Φι of the first portion 74 and a radial thickness "t". The insulation sleeve 90 can be made from any thermally insulating material, such as a ceramic or glass/silica fiber.

[0031 ] The insulation sleeve 90 is inserted into the second portion 76 of the heat exchanger section 22 until one end adjacent the opening 94 abuts or is in close proximity with the neck 78. The other end of the insulation sleeve 90 adjacent the opening 92 is aligned with the opening 43 in the vestibule panel 40. The insulation sleeve 90 is held in place by friction with the second portion 76, the neck 78, and/or the gasket 60. As a result, the openings 92, 94 of each insulation sleeve 90 are aligned with an opening 43 in the vestibule panel 40, an opening 62 in the gasket 60, and one of the second portions 58 of the burner 50 (see Fig. 2B).

[0032] The third diameter Φ ₃ and thickness t of the insulation sleeve 90 are configured such that when the insulation sleeve is provided within the second section 76, the sleeve radially abuts the wall 70 and the sleeve passage 91 is longitudinally aligned with the first portion 74. As a result, there is no radial air gap between the insulation sleeve 90 and the wall 70. The radially innermost structure within the section 22 - either the insulation sleeve 90 material or the wall 70 inner surface of the first section 74 - has a substantially constant diameter.

[0033] As shown in Fig. 8, in operation flames F emanating from each second portion 58 extend through the associated opening 62 of the gasket 60, the opening 43 in the vestibule panel 40, and into the opening 25 at the inlet end 24 of the associated heat exchange section 22. The flames F are tailored such that the tip of each flame terminates at or adjacent to the opening 25 in the inlet end 24 of each section 22, i.e., the flames may barely extend into the interior of each tube and therefore barely extend into the insulation sleeve 90. Alternatively, it will be

appreciated that the insulation sleeve 90 described herein can be omitted from one or more of the inlet ends 24 (see Fig. 9) and, thus, the flame F would barely extend into the second portion 76 of the inlet end 24.

[0034] When the burner 50 is a premixed burner, the very short flame F and rapid release of heat can cause the vestibule panel 40 and/or inlet ends 24 of the heat exchanger sections 22 to overheat. The sleeve 90 of the present invention helps alleviate these overheating concerns by providing insulation within the inlet ends 24 of the heat exchanger sections 22.

[0035] In particular, the insulation sleeve 90 described herein helps protect the material forming the inlet end 24 from thermal damage due to the increased heat provided by the pre- mix/low NO _x burner 50. That said, the length of the second portion 76 and the length of the insulation sleeve 90 can be tailored to provide a desired degree of temperature

reduction/protection within the inlet end 24. Where the insulation sleeve is omitted in Fig. 9, the expanded second portion 76 helps protect the smaller diameter first portion 74 by providing enough space near/around the flame such that the wall 70 is not damaged or heated beyond its rating/allowable limit.

[0036] Furthermore, an abrupt change in the inner diameter along the inlet end 24 could cause overheating within the inlet end as well as turbulence for combustion products flowing therethrough. By providing the inlet end 24 of each section 22 with a substantially constant inner diameter Φι the abrupt diameter change is avoided and no increase in pressure occurs at the transition between the insulation sleeve 90 and the neck 78.

[0037] What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.