Thermal conductivity of nanoparticle suspensions in insulating media measured with a transient optical grating and a hotwire

The thermal conductivities of nanoparticle suspensions of Al2O3 in C10H22 (decane) and isoparaffinic polyalphaolefin (PAO) have been measured using two dissimilar techniques: a transient hotwire measurement based on the heat loss and resistivity of a heated wire in solution, and the thermal decay of a transient grating generated by the interference of two picosecond light pulses. Agreement between the two techniques is good, indicating that either is a reliable way for measuring the thermal conductivity of colloidal suspensions. Suspensions with volume concentrations from 0.125% to 1% were measured. The Al2O3 particles were suspended by means of surfactants added to the base fluids and sonication. The thermal conductivity of the suspensions was greater than expected from classical continuum models, with a greater enhancement observed in decane than in PAO. (c) 2008 American Institute of Physics.