The importance of thermodynamic and phase behavior of working fluids embedded with nanostructured materials is fundamental to new nanotechnology applications. Considering the extremely large number of different both nanoparticle types and reference fluids, it is obvious that there is need for developing theoretically sound methods of the prompt estimation thermodynamic properties and phase equlibria for emerging working media. The effect of nanoparticles on the critical point shift for classical fluids doped by nanoparticles is examined. Global phase diagrams of two-component fluids with nanoparticles are analyzed. The global phase diagram studies of binary mixtures provide some basic ideas of how the required methods can be developed to visualize the phase behavior of nanofluid blends. The mapping of the global equilibrium surface in the parameter space of the equation of state (EoS) model provides the most comprehensive criteria for predicting binary nanofluid phase behavior. Results of calculations of phase equilibria for some nanofluids are described..