Effects of thermal property variations on the liquid flow and heat transfer in microchannel heat sinks

Three-dimensional conjugate numerical simulations using the inlet, average and variable thermal properties respectively were performed for the laminar water flow and heat transfer in rectangular microchannels with D-h of 0.333 min at Re of 101-1775. Both average and variable properties are adopted in data reduction. The calculated local and average characteristics of flow and heat transfer are compared among different methods, and with the experiments, correlations and simplified theoretical solution data from published literatures. Compared with the inlet property method, both average and variable property methods have significantly lower f(app), but higher convective heat transfer coefficient h(z) and Nu(z) Compared with the average property method, the variable property method has higher f(app)Re(ave) and lower h(z) at the beginning, but lower f(app)Re(ave) and higher h(z) at the later section of the channel. The calculated Nu(ave) agree well with the Sieder-Tate correlation and the recently reported experiment, validating the traditional macroscale theory in predicting the flow and heat transfer characteristics in the dimension and Re range of the present work. (C) 2007 Elsevier Ltd. All rights reserved.