11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) E. O˜ nate, J. Oliver and A. Huerta (Eds) UNSTRUCTURED 3D NUMERICAL MODELING OF THE MELTING OF A PCM CONTAINED IN A SPHERICAL CAPSULE Pedro A. Galione 13 , Oriol Lehmkuhl 12 , Joaquim Rigola 1 , Carles D. P´ erez-Segarra 1 , Assensi Oliva 1 1 Heat and Mass Transfer Technological Center (CTTC),Universitat Polit` ecnica de Catalunya - BarcelonaTech, ETSEIAT, Colom 11, 08222, Terrassa (Barcelona), Spain. 2 Termo Fluids S.L., Av. Jacquard 97 1-E, 08222, Terrassa (Barcelona), Spain. 3 Instituto de Ingenier´ ıa Mec´anica y Producci´on Industrial (IIMPI), Universidad de la Rep´ ublica (UdelaR), Uruguay. Key words: Multiphysics Problems, Computing Methods, Melting, PCM Abstract. 1 INTRODUCTION Fixed-grid enthalpy models have been used extensively for solid-liquid phase-change computational fluid dynamics (CFD) simulations. Generally, implicit time schemes are used by most authors [1, 2]. Tan et al. [2] presented an experimental and numerical study of the melting of a phase change material (PCM) contained in a spherical capsule; where a two-dimensional (2D) model was used for the numerical simulations, assuming axisymmetry with respect to the vertical axis. This work is a continuation of an earlier work [3], which dealt with fixed-grid solid-liquid phase-change modeling using explicit time schemes, specially suited for its combination with turbulence models for simulation of the fluid motion. Here, the numerical model is applied for both 2D and 3D simulations of the experiment of Tan et al., using unstructured meshes. The 3D treatment allows to reproduce 3D flow patterns that are not simulated with the 2D models. Some modifications to the numerical treatment presented in [3] have been necessary, in order to avoid numerical divergence in cases where dense meshes were used. These changes are related to the treatment of the momentum equation in the solid-liquid interface. A formulation where both liquid and solid phases are assumed to have the same thermo- physical properties, as well as another which accounts for their variation with phase and temperature (i.e. expansion in the melting, variation of conductivity, etc.), are numerically solved and their results compared. 1