On the stability of nanofluid ice slurry produced via impinging stream method under thermal and phase-change cycles

Nanofluid ice slurry has shown promising potential due to superior heat transfer and lower supercooling degree. The stability of the nanofluid ice slurry is of paramount importance to ensure high performance for practical applications. This study evaluates the stability (flow and thermal properties) of nanofluid ice slurry produced via a dynamic, impinging-stream method and compares with its conventional counterpart, i.e., the static, non-impinging-steam approach. Thermal cycling (heating-cooling) with phase change (freezing-thawing) cycles were carried out to measure absorbance, thermal conductivity, and viscosity. The results showed that when using the method of producing nanofluid ice slurry by impinging flow, nanofluid ice slurry with concentrations of 0.1, 0.2, and 0.3 w.t.% decreased in absorbance by 17%, 21%, and 26%, in thermal conductivity by 0.5%, 1.4%, and 2.17%, and in viscosity by 3.6%, 5.3%, and 10.4%, respectively, after nine freezing and thawing cycles. Additionally, for instance, for a nanofluid with a concentration of 0.2 w.t%, after 9 phase change cycles, the decrease in absorbance of the nanofluid solution using dynamic cycling was 7.1, 3.7, and 1.6 times higher than that of static cycling with an IPF of 25%, 50%, and 75%, respectively (thermal conductivity 4.1, 2.4, and 1.4 times; viscosity 2.8, 1.8, and 1.3 times). Higher nanoparticle concentration reduces the stability of the nanofluid ice slurry; the degree of reduction is first increased and then stabilized after six cycles. It was found that the dynamic method had an impact on the stability of the nanofluid compared with the static approach. Furthermore, empirical correlations were developed to predict the thermophysical properties based on phase-change cycles for practical applications.