Boussinesq approximation and thermal conductivity
 

I have used Boussinesq approximation for density in my simulation and taken all properties as constant except for thermal conductivity. Thermal conductivity is taken as linearly varying from solid to liquid phase.


Is using Varying thermal conductivity valid with Boussinesq approximation?
(PS:My Nusselt Number graphs look quite different from those of my colleagues with constant thermal conductivity)