Numerical study of melting and heat transfer of PCM in a rectangular cavity with bilateral flow boundary conditions

The melting of phase change material (PCM) in a rectangular cavity with heat transfer fluids (HTFs) flowing at both sides from bottom up (bilateral flow boundary conditions) are numerically studied. A parametric study is performed by changing the Reynolds number (Re) of HTF in a range of 1 x 10(4), 3 x 10(4), 5 x 10(4), 7 x 10(4) and the Rayleigh number (Ra) in a range of 3 x 10(6), 4 x 10(6), 5 x 10(6), 6 x 10(6). The results show that the formation of natural convection is due to the impacts of non-uniform heat transfer of HTF and cooling between solid-liquid interface and liquid PCM. The asymmetric flow boundaries lead to various skew forms of the PCM melting process and effect the heat transfer and thermal energy storage. The melting process can be divided into three melting stages, the first two stages are mainly ruled by Re and the last stage by Ra. A set of introduced dimensionless parameters are analyzed to elaborate the heat transfer mechanism and the general rule of melting characteristics. The various dimensionless correlations are applied to describe the evolution of melting volume fraction, dimensionless average temperature and thermal energy storage fraction during the melting process.