Correlations are presented for the viscosity and thermal conductivity of nonpolar, polar, and associating fluids over the wide ranges of PVT states. Empirically correlated density-dependent functions were developed to extend the kinetic gas theory to include dense fluids. Extensive comparisons with experimental data of pure fluids are made. The average absolute deviation is 4% for viscosity predictions and 6% for thermal conductivity predictions. The conformal solution model mixing rules have shown to yield predictions of viscosity and thermal conductivity for nonassociating mixtures of sufficient accuracy for most industrial uses. The viscosity and thermal conductivity predictive procedure is simple and straightforward. It requires only critical constants and acentric factors for nonpolar fluids. For polar and associating fluids, the dipole moment and an empirically determined association parameter, in addition, are required.

Understanding and predicting the behavior of water, especially in contact with various surfaces, is a scientific challenge. Molecularlevel understanding of hydrophobic effects and their macroscopic consequences, in particular, is critical to many applications. Macroscopically, a surface is classified as hydrophilic or hydrophobic depending on the contact angle formed by a water droplet. Because hydrophobic surfaces tend to cause water slip whereas hydrophilic ones do not, the former surfaces can yield self-cleaning garments and ice-repellent materials whereas the latter cannot. The results presented herein suggest that this dichotomy might be purely coincidental. Our simulation results demonstrate that hydrophilic surfaces can show features typically associated with hydrophobicity, namely liquid water slip. Further analysis provides details on the molecular mechanism responsible for this surprising result.P rotein folding (1), micelle and cellular membrane formation (2), and frictionless flow of water through carbon nanotube membranes (3-5) are only some manifestations of hydrophobic effects. Flat surfaces are arbitrarily classified as hydrophobic when a water droplet yields a contact angle larger than 90°, hydrophilic otherwise. A now famous 2008 commentary by Granick and Bae (6) initiated a scientific discussion to identify the molecular signature of hydrophobic vs. hydrophilic surfaces. The question is whether or not molecular properties exist for interfacial water molecules that change with the surface "degree of hydrophobicity." Identifying such properties could advance practical applications (e.g., designing self-cleaning surfaces) as well as fundamental scientific endeavors including understanding self-assembly (7).Molecular simulations should allow the discovery of such molecular signatures because they allow a systematic variation of the properties of a surface, as well as of surface-water interactions (8). Although the resultant substrates may not be realistic, the results are useful to interpret nature and to design innovative materials. It has so far been possible to relate some macroscopic observables to the degree of hydrophobicity [i.e., contact angle to adsorption free energy (9)]. Garde and coworkers employed equilibrium molecular dynamics (MD) to determine a number of quantities, including local density, contact angle, and adsorption of small solutes for water near surfaces of varying degrees of hydrophobicity (10). Whereas the local water density provided unsatisfactory characterization, the probability of cavity formation was found to be large near hydrophobic and small near hydrophilic surfaces.The present work focuses on the relation between one important macroscopic signature of hydrophobic surfaces, the hydrodynamic liquid slip, to molecular interfacial water properties. Large liquid slip on hydrophobic surfaces could reduce the drag in vessels navigating the seas, the pressure drop encountered by fluids flowing inside pipes, and even repel ice formation. Liquid slip seems to appear when ...

The computer solution involves selecting a dimensionless force F* and stepping down the spinline in small increments of **, determining V*{x*) at each point by a trial-and-error procedure so as to satisfy eq A-2.Literature Cited

A review of the characteristics of hydrophobicity is presented, with the goal of investigating the relationship, if any, between the contact angle (a macroscopically observed property) and the slip length (a microscopic phenomenon). An analysis of simulations, and of their evolution through the years, sheds light on some inherent differences between contact angle and slip length behavior on flat and patterned surfaces. Previous studies lead to the conclusion that epitaxial layering of fluid near the solid is intricately related to the magnitude of fluid slip. Epitaxial layer data help to explain unexpected slip length behavior in relation to the contact angle, and reported inconsistencies between slip length experiments and simulations. Therefore, it seems that solids that can produce favorable epitaxial layering of the fluid will cause larger slip. Dimensional analysis is used to elucidate the contact angle-slip length relationship. Results can be applied to the development of artificial supersolvophobic surfaces that would exhibit predictable fluid slip with important practical applications.

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