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Description:
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Heat transfer and fluid flow are studied numerically for a repeating microchannel
array with water as the circulating fluid . Generalized transport equations are discretized
and solved in three dimensions for velocities , pressure , and temperature . The SIMPLE
algorithm is used to link pressure and velocity fields , and a thermally repeated boundary
condition is applied along the repeating direction to model the repeating nature of the
geometry . The computational domain includes solid silicon and fluid regions . The fluid
region consists of a microchannel with a hydraulic diameter of 85 .58μm . Independent
parameters that were varied in this study are channel aspect ratio and Reynolds number .
The aspect ratios range from 0 .10 to 1 .0 and Reynolds number ranges from 50 to 400 . A
constant heat flux of 90 W /cm2 is applied to the northern face of the computational
domain , which simulates thermal energy generation from an integrated circuit .
A simplified model is validated against analytical fully developed flow results
and a grid independence study is performed for the complete model . The numerical
results for apparent friction coefficient and convective thermal resistance at the channel
inlet and exit for the 0 .317 aspect ratio are compared with the experimental data . The
numerical results closely match the experimental data . This close matching lends credibility to this method for predicting flows and temperatures of water and the silicon
substrate in microchannels .
Apparent friction coefficients linearly increase with Reynolds number , which is
explained by increased entry length for higher Reynolds number flows . The mean
temperature of water in the microchannels also linearly increases with channel length
after a short thermal entry region . Inlet and outlet thermal resistance values
monotonically decrease with increasing Reynolds number and increase with increasing
aspect ratio .
Thermal and friction coefficient results for large aspect ratios (1 and 0 .75 ) do not
differ significantly , but results for small aspect ratios (0 .1 and 0 .25 ) notably differ from
results of other aspect ratios . |