On the Possibility of a Radical Increase in Thermal Conductivity by Dispersed Particles

Abstract Theoretical and experimental data on the effect of additions of micro- and nanosized solid particles on the thermal conductivity of liquid media (nanofluids) are considered. According to theoretical calculations, a manifold increase in the thermal conductivity is possible only for resting media in which percolation structures are formed from the modifier nanoparticles, whereas in the case of the coolant circulation and/or random distribution of particles in its volume the increase in the thermal conductivity cannot increase several tens of percents. The primary factors for increasing the thermal conductivity are high volume fraction of particles and isotropicity of their properties, whereas the specific thermal conductivity of the particle material is not a key factor. The available experimental data were obtained using different measurement methods and different dispersions whose structure was not duly controlled. Therefore, the data are characterized by large scatter, which does not allow unambiguous identification of the acting averaging law, although the majority of data are characterized by positive deviation from Maxwell’s law. On the other hand, the available data do not exceed the values expected on the basis of the rule of logarithmic additivity of the component thermal conductivities.