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U.S. Department of Energy
Office of Scientific and Technical Information

Combustion gas heat recovery apparatus

Patent ·
OSTI ID:5745855

A secondary heat exchanger is positioned within a cold air return plenum of a forced air gas or oil fired furnace to preheat cold air drawn into the furnace through the cold air plenum. A heat recovery flue pipe is connected between a primary flue pipe of the furnace and the secondary heat exchanger, and an exhaust pipe is connected between the secondary heat exchanger and the outside of a structure served by the furnace. A secondary blower coupled to the exhaust pipe draws hot combustion gases from the primary flue pipe through the heat exchanger and exhausts cooled combustion gases to the outside. The secondary heat exchanger comprises a combustion gas inlet plenum and a combustion gas outlet plenum, with a plurality of heat conducting pipes sealingly connected therebetween. Each of the heat conducting pipes is arranged to define a circuitous path between the inlet plenum and the outlet plenum, with each heat conducting pipe defining at least two aligned linear radiating surfaces over which cold air is drawn. Heat conducting fins are intimately connected to the heat conducting pipes and a condensate drain is provided in the lower extremities of the heat conducting pipes to drain condensate from the secondary heat exchanger.

Assignee:
IFI; EDB-86-101826
Patent Number(s):
US 4558689
OSTI ID:
5745855
Country of Publication:
United States
Language:
English