This paper investigates heat transfer enhancement by means of additively manufactured static mixers during liquid water cooling of a horizontal, heated flat plate. The static mixers disrupt the thermal boundary layer and induce mixing, resulting in an increased heat transfer rate of about 2X larger than flows without mixers. Simulations of the flows provided insights into the flows near the mixers, and guided selection of specific mixer geometries. The mixers were fabricated directly into the flow channels using additive manufacturing and then assembled onto the heated plate. Two types of mixing structures were analyzed: twisted tape structures that are similar to conventional static mixers; and novel chevron shaped offset wing structures. Heat transfer performance was measured for liquid water (510 <= Re <= 1366) cooling the heated section with convective heat flux ranging between 0.1 and 0.8 W/cm(2). This work demonstrates the potential of additive manufacturing to enable novel flow geometries that can enhance convection heat transfer whilst minimizing pressure drop penalties and volumes. (C) 2019 Elsevier Ltd. All rights reserved.