Fouling in silicon microchannel designs used for IC chip cooling and its mitigation

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Title: Fouling in silicon microchannel designs used for IC chip cooling and its mitigation
Author: Perry, Jeffrey L.
Abstract: Particulate fouling studies with alumina and silica dispersions were performed in silicon, rectangular microchannels having hydraulic diameters between 220-225 μm. The particulates used ranged from the colloidal size range up to tens of microns in size (for particle aggregates). Data show for the most part the absence of particle depositions within the microchannels. This is even the case when there is an electrostatic attraction between the particles and the microchannel surface. The primary reason for this is due to the high wall shear stress at the microchannel walls. In contrast, the headers for the microchannels are quite susceptible to particulate fouling under the same conditions. This is because the shear stress at the surface is lower. This fouling within the header, however, does not provide an increase in pressure drop within the microchannel device. Moreover, depositions within the header region can be mitigated with proper pH adjustment. There is a secondary effect in particulate fouling when fibrous elements exist within the particle dispersion. The fouling behavior due to fibrous material is quite different. In fact, the presence of fibers is extremely detrimental to pressure drops within a microchannel device. A multi-scale force balance model for particulate fouling is developed. It uses conventional theories on the forces between a particle and a wall which are extended to particulate fouling within a microchannel device. The model covers a scale spanning several orders of magnitude. In addition, it includes van der Waals forces, electrostatic forces, fluidmechanics- related forces due to shear/lift, and a body force due to gravity.
Record URI: http://hdl.handle.net/1850/6211
Date: 2007-10

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