Influence of thermal cycling on stability and thermal conductivity of nanofluid ice slurry

Abstract

Nanofluid ice slurry has the advantages of large phase change latent heat, high energy storage density and cooling rate. In this article, a two-step approach was used to prepare water-based graphene oxide (GO), Al2O3, and GO-Al2O3 hybrid nanofluids. The effects of thermal cycling on the stability and thermal conductivity of nanofluid ice slurry were also investigated. Moreover, thermal conductivity model considering thermal cycling and mass fraction was proposed. Results show with the increase of the number of phase change cycles, the stability of nanofluids decreases gradually, and tends to be stable after 6 cycles. The lower the minimum temperature of the thermal cycling, the more serious the segregation of nanoparticles, the worse the stability of nanofluids after thermal cycling. In addition, multi-cycle of phase change has less influence on thermal conductivity of GO nanofluid than that of non-phase-change, although the influence is a little larger at the dilute concentration range. The thermal conductivity of GO-Al2O3 hybrid nanofluid ice slurry is between that of GO and Al2O3 aqueous single nanofluid after phase change thermal cycling. The influence of the phase change cycles on thermal conductivity decreases with the increase of concentration, however, the smaller the concentration, the larger the thermal conductivity reduction. The hybrid nanofluid ice slurry can ensure the dispersion stability and thermal conductivity of the fluid, and its comprehensive performance is better than that of nanofluid with one type of nanoparticle.