A thermal conductivity model for low concentrated nanofluids containing surfactants under various dispersion types

Various thermal conductivity models for nanofluid have been proposed, however, none have included the effect of the surfactant. In this paper, a thermal conductivity model which includes the effects of the interfacial layer formed by the surfactant and liquid molecules is proposed by upgrading Leong et al.ʹs model (2006). Based on the analysis of dispersion types, the thickness of the interfacial layer is defined by the length of the surfactant molecule for nanofluid under monolayer adsorption dispersion and double lengths of the surfactant molecule for nanofluid under electric double layer (EDL) adsorption dispersion. The length of the surfactant molecule is obtained by analyzing the stereo-chemical structure and assuming it is fully extended when adsorbed on the surface of the nanoparticle. The present model was compared with some experimental data for low concentrated nanofluid containing surfactants. The comparison results show the present model, in general, produces higher accuracies and precisions.