An experimental study is carried out to investigate the effect of inclination angle on the thermal performance of a flat-type heat sink. Heat sinks without and with PCM are examined comparatively. The range of inclination angle from theta= 0 degrees (vertical) to theta= 90 degrees (horizontal) is considered. N-eicosane with a melting range of 35-37 degrees C is used as PCM. Temperatures are measured to characterize the heat transfer in air and PCM domains. In addition, an imaging technique is used to visualize the movement of melting interface. The results obtained show that the inclination angle has a remarkable effect on the thermal performance of the PCM-based heat sink while its effect is negligible for the one without PCM. (C) 2017 Elsevier Ltd. All rights reserved.