Nanofluids are considered to be attractive as heat transfer fluids (HTF) and thermal energy storage (TES) for concentrated solar power (CSP) applications. Solvents doped with relatively low concentrations of nanoparticles (with diameters up to 100 nm) are termed as nanofluids. Numerical models for exploring the forces experienced by the nanoparticles are needed in order to ascertain the transport processes responsible for the anomalous material properties of the nanofluids that are observed in experimental measurements.
In this study a multiscale approach to modeling the forces acting on these particles was performed and the dynamics of transient nanoparticle agglomeration have been explored. The validity of the multiscale approach is demonstrated by examining a pair of nanoparticles in a fluid. The force interactions due to the presence of the electric double layer (EDL) were identified as a significant factor in determining the propensity for agglomerative of the nanoparticles. Simulations were performed to demonstrate the clustering and agglomeration of an ensemble of nanoparticles. The simulation results provide an estimate for the time scale for the agglomeration and the resultant structure of the agglomerated ensemble of nanoparticles. Subsequently simulations were performed using this numerical model corresponding to the available experimental data in the literature. The predictions from the numerical simulations show that the change in zeta potential (determined in part by the pH of the solvent phase) is a crucial parameter that affects the level of agglomeration of the nanoparticles. Finally, the numerical scheme is extended for performing true 3-D simulation. This approach is more sophisticated than the contemporary schemes that are reported in the literature that project 3-D forces on to a 2-D plane.