An experimental study of heat transfer in microchannel with pillar/pillars was conducted with air. Area-averaged temperature was measured by a I x 1 mm(2) resistance temperature detector (RTD), and data were collected over the range 100 <= Re <= 5600. The microchannel with a pillar had a heat transfer coefficient that was twice that of the channel without a pillar. Among the three geometric shapes of pillar studied, triangular pillar performed the best with 17.7 <= (Nu) <= 88.9. Micro particle image velocimetry (mu PIV) was used to measure the velocity field in the mircochannel and turbulent kinetic energy (TKE) calculation provided a measure of flow mixing. It was shown that TKE is closely related to the thermal performance and can be used to predict the Nusselt number. (C) 2013 Elsevier Ltd. All rights reserved.