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Kasibhatla, Raghavendra Rohith ; König-Haagen, Andreas ; Brüggemann, Dieter:
Numerical Modelling of Wetting Phenomena During Melting of PCM.
In: Procedia Engineering.
Bd. 157
(2016)
.
- S. 139-147.
ISSN 1877-7058
DOI: https://doi.org/10.1016/j.proeng.2016.08.349
Abstract
Latent heat thermal energy storage (LHTES) units using phase change material (PCM) exhibit a high thermal capacity, but also a low charging and discharging power. Macro-encapsulation of PCM is one way of enhancing the heat transfer rate in thermal storage units. During encapsulation, the cavity left to reduce mechanical stresses in the macro capsule, locks air. This makes the capsule a multiphase system consisting of immiscible phases namely PCM and air. Numerical modelling of a PCM capsule enables a detailed understanding of the phase change process of the PCM under the influence of air. In this article, two immiscible fluids PCM and air have been modeled using a continuum surface force (CSF) model in the open source computational fluid dynamics (CFD) software, OpenFOAM. The wetting of the melted PCM on the capsule wall is taken into account by implementing a contact angle boundary condition. The surface tension of the PCM with air is just contributed to the liquid phase of the PCM. The nonlinear enthalpy-temperature relation during the phase change is taken into consideration by a source-based fictitious method. The flow in the solid phase of the PCM is ramped down by considering a high solid viscosity. Experimental results are employed to validate the overall model. The results obtained from the complete numerical model have shown a great acceptance when compared with experiments. Despite several small deviations in the results, the numerical modelling is a potential tool to optimize the efficiency of thermal storage units.