Effect of Particle Agglomeration on Thermal Conductivity of Solar Salt Nanofluids

ObjectivesNanofluid technology is an important means to improve the thermal conductivity of energy storage materials in solar thermal power plants. However, the nanoparticles in actual molten salt based nanofluid usually aggregate and settle down, which significantly affects the thermal performance of the composites. To gain a deeper insight into the variation of thermophysical properties of molten salt based nanofluids, the silica nanoparticles with different aggregation morphologies were constructed in solar salt.MethodsThe effects of system temperature, mass fraction of nanoparticles, and micromorphology of aggregates were investigated based on the molecular dynamics simulation and lattice Boltzmann method.ResultsIt is found that the inclusion of nanoparticles can effectively enhance the thermal conductivity of the base fluid. Compared with the uniformly dispersed nanofluid, the heat conduction performance of the aggregated nanofluid is better, and it decreases with the increase of fractal dimension of agglomerates. Moreover, the thermal conductivity of nanofluid is negatively correlated with temperature and aggregate size, and positively correlated with mass fraction of nanoparticles, backbone length of each aggregate and degree of agglomeration.ConclusionsThe research results reveal the mechanism of nanoparticle aggregation on the heat transport within phase change materials and provide critical reference on the design of thermophysical properties of molten salt based nanofluids.