Air-to-air heat exchanger core

A core assembly for use in an air-to-air heat exchanger, said core comprising:

• a plurality of square plates, each plate comprising:
• an identical square planar central region;
• a first pair of flexible opposed flanges bent in a first direction with respect to said central region to form approximately a 90 degree angle with the central region;
• a second pair of flexible opposed edge flanges bent in a direction opposite said first direction with respect to said central region to form approximately a 90 degree angle with the central region;
• wherein said core is formed by said plurality of square plates that are positioned into a stack of parallel plates such that the opposed flanges of one of said plurality of plates is located in contact with and inside mating opposed flanges of a plate directly adjacent thereto such that the opposed flanges of said one of said plurality of plates flexes inwardly and the mating opposed flanges of the plate directly adjacent flexes outwardly so that a seal is formed between the opposed flanges of the one plate and the mating opposed flanges of the plate directly adjacent thereto, thereby forming a plurality of air passages between adjacent plates such that two perpendicular air pathways are formed in an interleaved orientation;
• frame means in contact with a bottom plate in said stack and a top plate in said stack for holding said plurality of plates in position.