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 Dh of 0.333 mm 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 fapp, but higher convective heat transfer coefficient hz and Nuz. Compared with the average property method, the variable property method has higher fappReave and lower hz at the beginning, but lower fappReave and higher hz at the later section of the channel. The calculated Nuave 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.