Gas Void Morphology and Distribution in Solidified Pure Paraffin Within a Cubic Thermal Energy Storage Unit

Donglei Wang, Qianqian Zhao and Rongzong Huang ()
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Donglei Wang: School of Energy Science and Engineering, Central South University, Changsha 410083, China
Qianqian Zhao: School of Energy Science and Engineering, Central South University, Changsha 410083, China
Rongzong Huang: School of Energy Science and Engineering, Central South University, Changsha 410083, China

Energies, 2025, vol. 18, issue 14, 1-12

Abstract: Gas voids inevitably form during the solidification of phase change materials (PCMs) due to volumetric contraction and thus deteriorate the thermal conductivity of solidified PCMs. In this work, the gas void morphology and distribution in solidified pure paraffin within a cubic thermal energy storage unit are experimentally studied. The three-dimensional structure of the solidified pure paraffin is reconstructed via computed tomography (CT) scanning with a resolution of up to 25 µm. Four distinct morphological types of gas voids are found, including irregular elliptical gas voids, elongated “needle-like” gas voids, micro gas voids, and large circular gas voids. The formation mechanisms of each type are analyzed. The morphology and distribution of gas voids indicate that the solidified pure paraffin structure is anisotropic. The effective thermal conductivity (ETC) of this solid–gas structure is numerically evaluated using lattice Boltzmann simulations, and a two-term power equation is fitted. The results show that the ETC in the vertical direction is significantly lower than in the horizontal direction and the ETC could be reduced by as much as 31.5% due to the presence of gas voids.

Keywords: gas void; phase change material; computed tomography scanning; lattice Boltzmann simulation; effective thermal conductivity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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