Numerical study of freezing of Cu-water nanofluid in a trapezoidal cavity

A numerical study has been carried out to investigate the solidification of a binary mixture of pure water and Cu nanoparticles inside a horizontal trapezoidal cavity of different dimensions under specific given boundary conditions for temperature and concentration gradients. The vertical side walls of the cavity are insulated while the top wall temperature is kept lower than that of the bottom wall. The effect of parameters such aspect ratio, initial temperature of the nanofluid, the cavity tilt angle, and Grashof number at the solidification time is investigated. The moving solid-liquid interface is obtained using Enthalpy-porosity technique in the model. We found that the solidification time decreases with the increase of the aspect ratio (i.e., a longer trapezoidal cavity). Aspect ratio is found to give a prominent effect. However, the effect of cavity tilt angle is found negligible on the solidification process. It was found that larger value of Grashof number decreases the solidification time in the square and trapezoidal cavity both, but increases the convective heat transfer in the trapezoidal cavity only. The results are useful for the development of latent heat thermal energy storage system for solar heat collector and for casting and mold design.