Numerical and Experimental Study of Solidification in a Spherical Shell

Abstract

The present study explores numerically and experimentally the process of a phase-change material (PCM) solidification in a spherical shell. At the initial state, the PCM liquid occupies 98.5% of the shell. The upper segment of 1.5% contains air, which flows in as the solidification progresses. In the experiments, a commercially available paraffin wax is used. Its properties are engaged in the numerical simulations. The investigation is performed for solidification in spherical shells of 20 mm, 40 mm, 60 mm, and 80 mm in diameter at the wall uniform temperature, which varied from 10°C to 40°C below the mean solidification temperature of the phase-change material. Transient numerical simulations are performed using the FLUENT 6.2 software and incorporate such phenomena as flow in the liquid phase, volumetric shrinkage due to solidification, and irregular boundary between the PCM and air. The numerical model is validated versus the experimental results. Shrinkage patterns and void formation are demonstrated. Dimensional analysis of the results is performed and presented as the PCM melt fractions versus the product of the Fourier and Stefan numbers. This analysis leads to a generalization that encompasses the cases considered herein.

Experimental Study of Vibration Effects on Heat Transfer during Solidification of Paraffin in a Spherical Shell

“…This optimum frequency was used for all other experiments in the study. The solidification time result of 30 minutes without vibration shown in Table 2 compares well with the numerical and experimental results presented by Assis et al [9], where the solidification time shown for 40 mm paraffin wax samples without vibration was approximately 36 minutes. The difference of 6 minutes may be due to the paraffin wax that was used by Assis et al [9], having had a lower solidfication temperature than the one used in this study by a difference of about 7°C.…”

“…Experiments were conducted with spherical geometries because a comparison (although limited) could be made to work presented by Assis et al [9], which studied the numerical and experimental solidification of paraffin wax, however, without vibration. One of the diameters studied was the same as in this study and therefore used for verification purposes.…”

A combined experimental and computational study on the melting behavior of a medium temperature phase change storage material inside shell and tube heat exchanger

“…They provided a correlation for the melting fraction versus an appropriate combination of the Grashof, Stefan and Fourier numbers. Also, they performed another combined experimental and numerical study on the solidification of PCM inside a spherical shell with various diameters [7]. Tan et al [8] conducted experimental and computational study on melting of PCM inside a spherical capsule.…”

Numerical Simulation and Optimization of the Melting Process of Phase Change Material inside Horizontal Annulus

“…The paraffin filled about 85% of the volume, while the remaining region was filled with air, modeled as compressible ideal gas, whose properties can also be found in Table 1. The thermal physical parameters used in this paper were taken from the reference [23]. RT27 had a liquidus temperature of 303 K and a solidus temperature of 301 K. Other relevant properties of the material were treated as constants in the fully solid or liquid state, but not as constants in the mushy zone, where they varied linearly with temperature, until they reached the constant value in the liquid and solid zones, as listed in Table 1.…”