Abstract: The effects of C-coated Cu nanoparticles on the rheological behavior of mirabilite phase change nanofluids with different mass fraction (1.0%, 1.5%, 2.0%, 3.5%, and 5.0%) at different temperatures were investigated. The viscosity of C-coated Cu nanoparticles phase change nanofluids was investigated at different shear rates (39.91~140 s^-1) and different temperatures (35~50 ℃). The results show that the hydrothermal method successfully prepares C-coated Cu nanoparticles. Nanofluid samples with mass fraction of 1.0% C-coated Cu nanoparticles at 35 ℃ and 1.5% C-coated Cu nanoparticles at 35, 40 ℃ exhibit Newtonian fluid behavior, but nanofluid samples exhibit non-Newtonian fluid behavior at other temperatures. When the mass fraction of C-coated Cu nanoparticles increases to 2.0%, 3.5% and 5.0%, the samples exhibit non-Newtonian fluid behavior, which conforms to the power law model. At the same time, the thermal properties of mirabilite composite phase change energy storage materials were studied. The composite phase change nanofluid has higher thermal conductivity, lower undercooling, and better cycle stability.

Key words: phase change energy storage material, C-coated Cu nanoparticle, mirabilite phase change nanofluid, viscosity, latent heat