In this study the inclined louvered fin, a hybrid fin design based on the slit fin and louvered fin design is considered. The goal of the research program is to investigate the interaction between the flow behaviour (flow deflection and transition to unsteady flow) and the thermo-hydraulics of the fin design. This approach was selected in order to reveal the flow physics behind the transitions found in the thermo-hydraulic data. Through flow visualization (dye injection in a water tunnel) the flow deflection and transition to unsteady flow was studied in different configurations and for varying Reynolds number. The flow deflection was quantified through the 'fin angle alignment factor'. Validated CFD simulations were used to further explore flow behaviour. In parallel, wind tunnel measurements were performed measuring the local heat transfer coefficients for the different louvers and the overall pressure drop. The impact of the fin pitch, fin angle and Reynolds number were studied. A comparison of both local and global parameters to the observed flow behaviour revealed the strong coupling between the flow and the thermo-hydraulics showing evidence of boundary layer driven flow. (C) 2010 Elsevier Ltd. All rights reserved.