A New Method for Analysis of Anomalous Increases in Thermal Conductivity of TiO2-Water Nanofluid

Thermal conductivity is an important characteristic of a nanofluid. This paper presents models for the prediction of the effective thermal conductivity of titanium oxide based on water by used of dimensionless groups. The models express the thermal conductivity of a nanofluid as a function of the thermal conductivity of interfacial shell, interfacial thickness and volume fraction. The model of effective thermal conductivity is divided into four regions by analysis of present models for the regions and can be obtained an effective value of dependence parameter. The model showed for volume fraction less than 1% and diameters less than 20 nm intensity of increase thermal conductivity is much more than other region. As we know, with decrease of concentration, the viscosity of nanofluid decreased, so this region is the best region for application of heat transfer devices because the pressure drop also decreased.