A comprehensive review of last experimental studies on thermal conductivity of nanofluids

In this paper, the last experimental results of the thermal conductivity of nanofluids have been investigated; therefore, because of the enormous numbers or some repetitions of such studies, it just tried to focus on those which had more acceptable results; however, it is not intended to present a systematic summary of the available references from the literature. All kinds of nanoparticles such as Al2O3, Fe3O4, TiO2, and CuO and their base fluids such as water, engine oil, glycol, and ethylene glycol have been investigated. The results showed that the effect of particle size of nanoparticle has a reversed impact on the value of thermal conductivity. To clarify, the thermal conductivity could increase by reduction in size of nanoparticles. On the other hand, the lower the suspension volume fraction is, the higher the thermal conductivity will be in nonlinear relation. Also the thermal conductivity and the temperature of the suspension have the direct influence on each other. In addition to the fact that a review paper has been prepared, the belief is to start this research with the scientific classification in order of all terms and expressions which have been used by previous scholars.