The performance of an enhanced microchannel heat sink with sectional oblique fins and with a coolant that contains Nano-Encapsulated Phase Change Material (NEPCM) particles is investigated using a 3D conjugated heat transfer model. Three volume fractions from zeta = 0 (pure water) to 0.3 are studied to investigate the effects of presence of NEPCM particles. Then the effects of introducing tip-clearance to the heat sink on thermal and hydrodynamic performance is examined at low Reynolds numbers (less than 215). Four values of tip-clearance to channel width ratio (t/W-c) are investigated ranging from a no gap (t/W-c = 0) to t/W-c = 0.74. On the bottom wall of the heat sink a range of uniform and fixed temperatures of 299.15 K to 340.15 K are applied. The cooling and hydrodynamic performance of the heat sink is studied using Nusselt and Euler numbers, respectively. It was observed that using of NEPCM slurry in contrast with pure water, enhanced the cooling performance of the heat sink but increased the Euler number. Furthermore, it was seen that the introduction of tip-clearance to the heat sink, if the clearance ratio is chosen properly, has the potential to enhance the cooling performance and reducing the Euler number simultaneously. (C) 2014 Elsevier Ltd. All rights reserved.