Air fin for a heat exchanger

An air fin for a heat exchanger, comprising:

• a plurality of corrugations defining air flow channels extending in a width direction of the air fin, said corrugations being defined by planar flanks joined by alternating crests and troughs;
• a plurality of first perforations extending through at least a portion of at least some of the flanks, the first perforations being arranged along a first plane oriented perpendicular to the width direction of the fin;
• a plurality of second perforations extending through at least a portion of at least some of the flanks, the second perforations being arranged along a second plane parallel to and spaced apart from the first plane;
• and
• a rectangular aperture extending through two or more consecutively arranged corrugations of the air fin, the rectangular aperture comprising a first edge aligned with the first plane and a second edge aligned with the second plane.