Rheem Manufacturing Company

Lin-Tao Lu

Diane M Jakobs

Keith M Grahl

Larry R Mullens

Ali Shenasa

Gallen W Stokes

A fuel-fired, forced air, draft induced heating furnace is provided with NOx reduction apparatus associated with a plurality of combustor tubes forming a portion of its heat exchanger structure. In-shot type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NOx reduction apparatus includes a plurality of metal mesh tubes having diameters substantially less than the internal diameters of the combustion tubes. Each metal mesh tube is coaxially anchored to and telescopingly over the outlet end of one of the burners and extends therefrom coaxially into the associated combustion tube. During burner operation the burner flames injected into the combustor tubes are forced through the mesh tubes which operate to laterally reduce the cross-sections of the flames, increase their axial velocity through the combustor tubes, and substantially diminish the intimate contact of secondary combustion air with the maximum temperature zones of the flames within the combustor tubes.

Low NO.sub.x combustion system for fuel-fired heating appliances

A tubular recuperative heat exchanger structure is mounted in a housing chamber within a fuel-fired condensing furnace in the vertical flow path of supply air being flowed through the housing by a blower. The heat exchanger structure comprises a primary heat exchanger defined by a vertically serpentined series of combustor tubes into open inlet ends of which a series of inshot-type fuel burners flow flames and hot combustion gases, and a secondary heat exchanger formed from a horizontally extending series of finned heat exchanger tubes having inlets in flow communication with the outlets of the combustor tubes and outlets in flow communication with the inlet of a draft inducer fan. The firing rate of the furnace is correlated to the configuration and relative geometries of the primary and secondary heat exchanger tubes in a manner making the overall heat exchanger highly compact and thermally efficient in addition to reducing air blower and draft inducer electrical consumption as well as reducing the operating noise of the furnace.

High efficiency fuel-fired condensing furnace having a compact heat

A fuel-fired, forced air draft induced heating furnace is provided with NO.sub.x reduction apparatus associated with a plurality of combustor tubes forming a portion of its heat exchanger structure. In-shot type fuel burners are spaced apart from and face the open inlet ends of horizontal combustion sections of the combustor tubes. The NO.sub.x reduction apparatus includes a plurality of metal mesh tubes having diameters substantially less than the internal diameters of the combustion tubes. The mesh tubes are coaxially supported within the combustor tubes, adjacent their inlet ends, by elongated support members longitudinally passing through the mesh tubes and having first ends anchored to the combustor tube inlet ends, and second ends slidably resting on internal side surface portions of the combustor tubes. During burner operation the burner flames injected into the combustor tubes are forced through the mesh tubes which operate to laterally reduce the cross-sections of the flames, increase their axial velocity through the combustor tubes, and substantially diminish the intimate contact of secondary combustion with the maximum temperature zones of the flames within the combustor tubes.

A fuel-fired condensing furnace is provided with a specially designed heat exchanger structure having a metal primary section and a plastic secondary or recuperative section. The primary section is defined by a horizontally spaced series of identically sized, vertically serpentined metal combustor tubes adapted to receive a throughflow of a burning fuel-air mixture discharged from the furnace burner section. Each tube has an essentially straight inlet combustion section sized to permit essentially complete combustion therein of the burning fuel-air mixture received by the tube, and a plurality of vertically spaced horizontal heat transfer sections that are horizontally flattened and narrowed to enhance their combustion heat transfer to supply air being forced upwardly through the furnace housing. The heat transfer efficiency of the flattened tube sections is further enhanced by forming spaced series of indentations in their flattened opposite side walls to create combustion gas flow turbulence within their interiors, and air flow turbulence along their exterior surfaces.

Serpentined tubular heat exchanger apparatus for a fuel-fired forced air

A high efficiency fuel-fired condensing furnace is provided with a compact recuperative heat exchanger structure comprising a metal primary heat exchanger positioned above and operatively connected to the inlet side of a secondary heat exchanger formed from a polyetherimide (PEI) plastic material. The primary heat exchanger is formed from a horizontally spaced series of vertically serpentined metal combustor tubes, and the second heat exchanger if formed from horizontally spaced apart injection molded inlet and outlet collector boxes interconnected by a horizontally spaced series of elongated hollow extruded plate members sealingly secured at their opposite ends to the collector boxes with the side edge-to-side edge widths of the hollow plate members being vertically oriented. The outlet ends of the metal tubes are operatively connected to the plastic inlet collector box. Cross-sectionally along their lengths, the hollow plastic plate members have horizontally flattened portions interdigitated with horizontally enlarged, convexly curved poritons. Various heat transfer-enhancing alternate embodiments of the hollow plate members are disclosed. Additionally disclosed is an alternate embodiment of the plastic secondary heat exchanger in which the inlet collector box is positioned atop the outlet collector box, and the hollow plate members are internally baffled in a manner causing combustion gas exiting the inlet collector box to make two passes through the hollow plate members before entering the outlet collector box.

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Fort Smith, AR, United States of America

Lin-Tao Lu