High efficiency fuel-fired condensing furnace having a compact heat exchanger system

摘要

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.