A heat exchanger includes a heat exchanger core. The heat exchanger core includes a first fin and a second fin. The second fin is spaced apart from the first fin. The heat exchanger core also includes a primary passage defined between the first fin and the second fin and extending through the heat exchanger core. The heat exchanger core also includes a plurality of airfoils extending through the first fin, the primary passage, and the second fin. At least one airfoil of the plurality of airfoils includes a secondary passage. The secondary passage extends through the heat exchanger core within the at least one airfoil transverse to the primary passage.