Predictions of flow and heat transfer in microchannels are ongoing issues ill microfludics. This work focused oil laminar flow (69 < Re < 800) within rectangular microchannel with hydraulic diameter from 106 pin to 307 pin for single-phase liquid flow. The friction factors obtained by experiments oil the microchannels showed that conventional theory for fully-developed flow is applicable within the range of our experiments. A manifold configuration Which ensured uniform flow through the microchannel array is thought to contribute to the improvement of accuracy. The average Nusselt number for the microchannel array was also evaluated experimentally in the condition of constant heat transfer rate. We found that there were deviations between the experimental and theoretical values of heat transfer rate in the microchannels. In order to predict heat transfer rate accurately, we proposed all empirical correlation in terms of Nu/(Re-0.62 Pr-0.33) and Brinkman number confined to the experimental range. The correlation is expected to be useful to design the microchannel devices related to heat transfer. (C) 2008 Elsevier Ltd. All rights reserved.