The characteristic of fluid flow and heat transfer in microchannel heat sinks was investigated theoretically and experimentally. Firstly

the theoretical model of convective heat transfer in the microchannel heat sink was presented. Secondly

the values of pressure drop and Nusselt number were measured and calculated based on the experiments. Furthermore

the experimental results were compared with those obtained from theoretical model

average error about 10%. Lastly

the conductive thermal resistance

convective thermal resistance and capacitive thermal resistance were also analyzed under different Reynolds numbers and aspect ratios of channel. Results indicate that

the convective thermal resistance plays an important role in the heat transfer performance of microchannel heat sinks

with the proportion about 90% when Reynolds number and aspect ratio of channel are 985 and 1

respectively; while the conductive thermal resistance can be neglected (less than 10%) under small Reynolds number

and the capacitive thermal resistance to total thermal resistance decreases with the increasing Reynolds number and aspect ratio of channel.