AGGREGATION AND EFFECTIVE THERMAL CONDUCTIVITY OF NANOFLUIDS: DEPENDENCE ON CLUSTER SIZE AND MORPHOLOGY

We combine a multipolar expansion technique and a cluster cluster aggregation algorithm to accurately compute the effect of aggregation on the thermal conductivity of nanofluids. Results show that the normalized enhancement in the effective conductivity of nanofluids exhibits a power law dependence on average cluster size. The exponent in the power law is a decreasing function of the fractal dimension, and is always larger than zero, thus predicting enhancements in excess of Maxwell's theory for well dispersed individual nanoparticles. Results are interpreted in terms of an effective particle size for heat conduction of aggregates which approximately scales as the gyration radius, specially at larger fractal dimensions.