| Abstrakt: |
The last decade has brought a growing number of studies about nanofluids as perspective working fluids with abnormally high thermal conductivity and a huge potential for intensifying heat and mass transfer. Despite the abundance of published research papers on nanofluid heat and mass transfer, the critical properties of these systems have been hardly considered at all. The key factors that determine the thermodynamic properties and the phase behavior of working fluids are the critical point for pure liquids and the critical lines for binary mixtures. Therefore, we have devised a thermodynamic model for estimating the impact of nanoparticles upon the shift of the critical point and the balance line between fluid and steam for traditional working fluids. Using the model, we have estimated the shift of the critical point for a classical working fluid-carbon dioxide-with additives of structured carbonic materials (nanotubes, fullerenes, and graphene flakes) and metal oxides (titanium and silicon dioxides as well as zinc and copper oxides). The research findings prove a positive shift of the critical temperature and density of the system point with increasing density of nanoparticle material. Knowing the critical point is as important as taking into account the characteristics of heat and mass transfer because addition of nanostructured materials changes both the thermal and dynamic surface of nanofluids and the topology of their phase behavior. [ABSTRACT FROM AUTHOR] |
