Accessing the Melting Dynamics of Phase Change Material Under Reduced Gravity Conditions

Phase Change Materials (PCMs) are widely used materials in thermal management applications. The passive working, good thermal stability and inherent thermophysical properties make PCM a natural fit for thermal control devices. However, their performance in real working conditions is often different from the behavior measured at lab scale owing to the effects occurring from varied heat sources, length scale, gravity forces, enthalpy and supercooling effects, etc. In this study, a two-dimensional computational fluid dynamic (CFD) model of a PCM-filled square enclosure with constant temperature bottom heating is developed to investigate the impact of reduced gravity on the melting process of PCMs and assess the dynamic characteristics that evolve with time. The control volume-based enthalpy porosity approach is utilized to simulate the melting process of paraffin-based PCM. Numerical simulations are carried out with reduced gravity environments by varying g to 0.2g. The evolution of flow regimes from conductive to convective through the destabilization of conductive state to the onset of Rayleigh-Benard convection, and chaotic flow is presented in terms of temperature and flow fields. It is found that when the gravity is reduced to 0.2g, the onset of convection delays by ∼ 3 times compared to the time taken by PCM under the standard gravity. In conclusion, the present study has provided valuable insights into the underlying physical phenomena of PCM melting in reduced gravity important in developing design strategies for PCM-based thermal energy storage systems that can operate effectively in reduced gravity environments.