Thermal Conductivity of Nanoparticle–Fluid Mixture

Effective thermal conductivity of mixtures of  uids and nanometer-size particles is measured by a steady-state parallel-plate method. The tested  uids contain two types of nanoparticles, Al2O3 and CuO, dispersed in water, vacuum pump  uid, engine oil, and ethylene glycol. Experimental results show that the thermal conductivities of nanoparticle– uid mixtures are higher than those of the base  uids. Using theoretical models of effective thermal conductivity of a mixture, we have demonstrated that the predicted thermal conductivities of nanoparticle– uid mixtures are much lower than our measured data, indicating the deŽ ciency in the existing models when used for nanoparticle– uid mixtures. Possible mechanisms contributing to enhancement of the thermal conductivity of the mixtures are discussed. A more comprehensive theory is needed to fully explain the behavior of nanoparticle– uid mixtures.