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A discrete computational approach based on molecular dynamics (MD) simulations is proposed for evaluating the latent heat of vaporization of nanofluids. The computational algorithm, which considers the interaction of the solid and the fluid molecules, is used for obtaining the enhancement of the latent heat of a base fluid due to the suspension of nanoparticles. The method is validated by comparing the computed latent heat values of water with standard values at different saturation temperatures. Simulation of a water-platinum nanofluid system is performed, treating the volume fraction and size of nanoparticles as parameters. The trends in the variation are found to match well with experimental results on nanofluids. Discussions are also presented on the limitations of the proposed model, and on methods to overcome them.

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Adhesive forces between two approaching asperities will deform the asperities, and under certain conditions this will result in a sudden runaway deformations leading to a jump-to-contact instability. We present finite element-based numerical studies on adhesioninduced deformation and instability in asperities. We consider the adhesive force acting on an asperity, when it is brought near a rigid half-space, due to van der Waals interaction between the asperity and the half-space. The adhesive force is considered to be distributed over the volume of the asperity (body force), thus resulting in more realistic simulations for the length scales considered. Iteration scheme based on a ''residual stress update'' algorithm is used to capture the effect of deformation on the adhesion force, and thereby the equilibrium configuration and the corresponding force. The numerical results are compared with the previous approximate analytical solutions for adhesion force, deformation of the asperity and adhesioninduced mechanical instability (jump-to-contact). It is observed that the instability can occur at separations much higher, and could possibly explain the higher value of instability separation observed in experiments. The stresses in asperities, particularly in case of small ones, are found to be high enough to cause yielding before jump-to-contact. The effect of roughness is considered by modeling a spherical protrusion on the hemispherical asperity. This small-scale roughness at the tip of the asperities is found to control the deformation behavior at small separations, and hence are important in determining the friction and wear due to the jump-to-contact instability.