Heat transport in silicon microchannel arrays

Investigations are conducted to understand the heat transport and fluid flow mechanisms in microchannel heat sinks. Single-phase experiments are performed with copper microchannels to explore the validity of classical correlations based on conventional-sized channels for predicting the heat transfer behavior in single-phase flow through rectangular microchannels. Numerical predictions obtained from computational fluid dynamics (CFD) analyses of the three-dimensional conjugate heat transfer process in a microchannel heat sink under classical, continuum assumptions were found to be in good agreement with the experimental data, suggesting that a conventional analysis approach can be employed in predicting heat transfer behavior in microchannels if the entrance and boundary conditions are correctly matched. In addition, simplified numerical analyses are conducted for laminar thermally developing flow in rectangular microchannels of various aspect ratios under circumferentially uniform wall temperature and axially uniform wall heat flux thermal boundary conditions. Based on the numerical results obtained, generalized correlations for predicting Nusselt numbers, useful for the design and optimization of microchannel heat sinks and other microfluidic devices, are proposed. Flow boiling in arrays of parallel microchannels is investigated using a silicon test piece with imbedded discrete heat sources and integrated local temperature sensors. Twenty five microsensors integrated into the microchannel heat sinks allow for accurate local temperature measurements and the determination of local heat transfer coefficients over the entire test piece. The experimental results have allowed a critical assessment of the applicability of existing models and correlations in predicting the heat transfer rates and pressure drops in microchannel arrays, and have led to the development of models for predicting the two-phase pressure drop and saturated boiling heat transfer coefficient