Treffer: New liquid fraction measurement methodology for phase change material analysis based on X-ray computed tomography.

To tackle climate change, it is of fundamental importance to develop more efficient systems to convert and manage energy. Latent Thermal Energy Storage (LTES) systems, which are based on Phase Change Materials (PCMs), present many interesting features that can lead us to achieve energy sustainability. In fact, these systems can be employed in many applications (e.g., HVAC, buildings thermal management, thermal energy recovery). To use PCMs, it is crucial to understand and monitor their phase-change behaviour. However, the evaluation of two-phase systems is still difficult because of the intrinsic complexity and transient behaviour. In the present study, a new methodology to measure liquid fraction is proposed. X-ray Computed Tomography (XCT) is used to follow the solidification process of eicosane. XCT and the acquisition settings were optimised to ensure maximum contrast between the phases. Then, the solidification process of eicosane was dynamically studied and the volumetric liquid fraction was extracted. Finally, via the Ansys Fluent software, a CFD model, based on the enthalpy-porosity method, was implemented to simulate the solidification of eicosane. The numerical results were compared against the experimental data, showing excellent agreement. This novel experimental methodology opens new possibilities to characterise and understand the solid-liquid phase transition process of PCMs, by directly observing and quantifying the solid/liquid phase evolution in time, the volumetric shrinkage, the presence of voids and the different phases that might occur during the phase-change process. • A combination of X-ray voltage and filter was optimised to yield the highest possible contrast between the solid and liquid eicosane phases. • Time-lapse X-ray computed tomography was used to scan the solidification process of eicosane. • Volumetric liquid fraction was extracted via Python image processing script, based on the Otsu thresholding method. • Enthalpy-porosity numerical method was successfully validated against the experimental volumetric liquid fraction. [ABSTRACT FROM AUTHOR]