Numerical study of melting process in an angled rectangular enclosure using the Lattice Boltzmann method

In this paper melting process of phase change materials (PCMs) in an inclined rectangular enclosure with different aspect ratios has been numerically investigated. The opted PCM is paraffin ( ) and the enclosure is assumed to be heated isothermally from one side, while all other sides are thermally insulated. To investigate the temperature and velocity fields, the enthalpy-based D2Q9 lattice Boltzmann method is used, while an immersed moving boundary condition scheme firstly implemented by Hung et. al is treated for the moving phase interface. Three aspect ratios of 0.5, 1.0 and 1.5 along with three inclination angles of 0°, 45° and 90° are investigated to study the melting process of paraffin at Rayleigh numbers of 104, 5×104, and 105. Results indicate that variation of the enclosure orientation angle is an easy and effective way to optimize the total melting time, yet, the most suitable orientation angle depends on aspect ratio as well. For aspect ratios lower than or equal to 0.5, increasing the inclination angle leads to higher melting rates, but there is an optimum inclination angle for higher aspect ratios. The optimum case for the common Rayleigh number of 5×104 is found to be a 90° enclosure with an aspect ratio of 0.5. In general, for all cases considered here, the total melting time of an enclosure with 45° inclination angle is always less than the horizontal enclosure