4D spatio-temporal visualization of solid volume fraction in molten sodium chloride during crystallization process by multi-layered thermal-resistive electrical resistance tomography (ml-trERT)

Abstract

Solid volume fraction ${}_{}{}^S\phi$ in molten sodium chloride (NaCl) during the crystallization proces has been visualized in 4D spatio-temporal (3D spatial + 1D temporal) by multi-layered thermal-resistive electrical resistance tomography (ml-trERT). In the ml-trERT, a total of 24 platinum wire electrodes (Pt-electrodes) were employed as melt-resistive sensors and arranged in a multi-layered configuration $\left(z=15\mathrm{mm},z=10\mathrm{mm},\text{and}z=5\mathrm{mm}\right)$ with eight electrodes per layer in the vicinity of a cylindrical alumina crucible as the container. As the results, the ${}_{}{}^S\phi$ in the molten sodium chloride was dynamically increase during the crystallization process ($1076.55K>T>1068.82K$). A significant increase in the spatially averaged solid volume fraction $\left({}_{}{}^S\phi \right)$ is observed at the beginning of the crystallization process, represents crystal nucleation. Subsequently, slight increase in the $\left({}_{}{}^S\phi \right)$ represents larger crystal formation which diffused from top to bottom layer. In order to validate the results by the ml-trERT, a qualitative and quantitative validation with transient enthalpy porosity (TEP) model were employed. According to the validation, the ml-trERT results are in a good agreement qualitatively and quantitatively with the TEP model with temporally averaged relative error ${\overline{\delta }}_{z=15\mathrm{mm}}=0.043$, ${\overline{\delta }}_{z=10\mathrm{mm}}=0.042$, and ${\overline{\delta }}_{z=5\mathrm{mm}}=0.054$.