why not FLUENT ? it gives opportunity of two-phase modeling nanofluids convective heat transfer by using three simples models: Eulerian, Mixture and VOF.
I did not use FLUENT since 2000. Firstly, the FLUENT had been under Ansys software and i need time to re-use it. Secondly, it is not easy to publish a paper on Q1 journals using FLUENT.. I am right or we can publish in Q1 journal.
Use empirical or experimental thermo physical properties correlations for finding density, viscosity, thermal conductivity etc. In comsol, use those values in material section.