Rheem Manufacturing Company

Ali Shenasa

Diane M Jakobs

Lin-Tao Lu

Gallen W Stokes

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

Ali Shenasa