Flue heat recovery device

In a flue heat recovery device for furnaces, including a flue gas chamber, a clean air chamber, and heat pipes for transferring heat from said flue gas chamber to said clean air chamber, the improvement comprising, in combination, a rectangular base tray having upturned edges on the long sides and one short end thereof, a three-sided member sealably secured at its bottom edges to said upturned edges at said one end of said base tray, a top plate secured to the top edges of said three-sided member, a corrosion-proof wall releasably and sealably engaged with the open side of said three-sided member and top plate and forming therewith a flue gas chamber, means defining a flue gas inlet opening in said base tray opening into said flue gas chamber for connection to a furnace, means defining a flue gas outlet opening in said top plate opening for connection to a chimney flue, a four walled, open-ended box member removably supported on the other end of said base tray between the upturned long side edges thereon with one of the walls thereof supporting on its exterior surface said corrosion-proof wall, said four-walled box member defining a clean air chamber having a clean air inlet opening at the top thereof, a clean air outlet opening in said base tray opening from the bottom of said clean air chamber, a fan supported on said base tray adjacent said outlet opening for flowing air through said clean air chamber, a plurality of parallel heat pipes supported by and extending through said corrosion-proof wall, a support plate interior of said box member for supporting said heat pipes, said pipes being inclined at an angle of at least about 10.degree. to the horizontal with the lower ends thereof in said flue gas chamber and the upper ends thereof in said clean air chamber, said clean air chamber and the heat pipes carried thereby being removable as a unit from said base tray.