Corrugated cooling fin with louvers

A corrugated heat exchanger fin (42) comprising a series of flat walls (44) integrally folded at alternating crests (46) with a predetermined fin wall width (W) measured between crests, said crests (46) being adapted to be bonded to parallel, flat heat exchanger tubes (20) so as to form fluid flow passages (F) enclosed between adjacent fin walls (44) and said tubes (20) through which a fluid is forced in a direction generally parallel to said crests (46) and with each fin wall (44) separating a pair of adjacent flow passages (F) from each other, each of said adjacent flow passages (F) also having a constricted area (C) within the inner surface of a crest (46) and an opposed unconstricted area (O) between the outer surfaces of two adjacent crests (46), characterized in that,

• each fin wall (44) is formed with a series of integral, substantially planar louvers (48) bent out of said wall (44), each of said louvers (48) having a length generally parallel to said fin wall (W) width, each louver being tilted out of and through the plane of its fin wall (44) about an oblique axis so as to move one diagonal half of said louver (48) substantially entirely to one side of said fin wall (44) and concurrently move the other diagonal half of said louver (48) substantially entirely to the other side of said fin wall (44), thereby moving diagonally opposed corners of said louver (48) into the unconstricted (O) areas of, and out of the constricted (C) areas of the adjacent flow passages (F) respective to each of said fin walls (44).