This study presents an investigation of a novel cross-corrugated primary surface for use in a heat exchanger and focuses on the design optimization of an anti-phase secondary corrugation which showed potential to improve the aero-thermal performance of a cross-corrugated heat exchanger in the accompanying paper Doo et al. [15]. In the present study, three-dimensional numerical simulations using steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations with a low-Reynolds number k-epsilon turbulence model were carried out for a range of parametric variations of the anti-phase secondary corrugation on a cross-corrugated geometry. The mechanism of enhancing the aero-thermal performance was subsequently investigated by careful analysis of the flow structures and thermal field as well as the analysis of the entropy generation in the flow passage. (C) 2013 Elsevier Ltd. All rights reserved.