Containerless nucleation behavior and supercooling degree of acoustically levitated graphene oxide nanofluid PCM

• Graphene oxide nanofluid drop was acoustically levitated and solidified.
• The supercooling degree of nanofluid drop can be reduced by 59.79%.
• Only on the upper or lower surfaces of the nanosheets can crystal nucleus form and grow.
• The nucleation rate increases significantly with the increasing of supercooling degree.

Acoustic levitation constitutes an alternative experiment technology for avoiding contamination from container walls or other external objects. Graphene oxide nanofluid drop was acoustically levitated and solidified, and supercooling degree of nanofluid drop at different cooling temperatures was measured. The supercooling degree of nanofluid drop can be reduced by 59.79% in comparison to that of the deionized water, and the reduction of supercooling degree gradually weakens with the decrease of cooling temperature. Based on Wenzel's wetting model, the authors established a new physical model of nanosheet to analyze the effect of rough surface on the nucleation behavior and supercooling degree, revealing that only on the upper or lower surfaces of the nanosheets can crystal nucleus form and grow, and nucleation on the thickness surface is difficult. Furthermore, a model for predicting nucleation rate of nanofluid was proposed, suggesting that the nucleation rate increases significantly with the increasing of supercooling degree.