The most crucial factor on the thermal conductivity of metal-water nanofluids: Match degree of the phonon density of state

Abstract

Nanoparticle addition with higher thermal conductivity can produce greater thermal conductivity of nanofluid based on the Maxwell effective medium theory. But some inconsistent and contradictory results can be found. To explore if nanoparticle additions with higher thermal conductivity are necessary for greater thermal conductivity of nanoifluids, different metal-water (gold-water, silver-water, copper-water and iron-water) nanofluids have been studied by dynamic molecular method. The results indicate that Au-water nanofluid posses greater thermal conductivity and thicker nanolayer due to the stronger interaction forces between Au-water molecules. In addition, an important index named match degree of phonon density of state (PDOS) is proposed and it is believed that the phonon match between metal and water molecules is the most crucial mechanism for elevating the thermal conductivity of metal-water nanofluids. A significant reference can be provided for the preparation of metal-water nanofluids with higher thermal conductivity. • The ETC for various metal-water is inconsistent with that predicted by effective medium theory. • Metal-water with thicker nanolayer tends to have higher thermal conductivity. • The match degree of PDOS of the metal-water is a crucial index for thermal conductivity.