A numerical study of the solidification of Erythritol phase change material (PCM) is performed with nano-enhancement in a thermal battery for waste heat recovery in the temperature range of 100°C–150°C. To capture this physical phenomenon, a novel one-domain continuum model is used in which a complete set of equivalent conservative governing equations are discretized using finite volume method and solved using an in-house developed code. The enthalpy-porosity technique is used to capture the phase change phenomenon. A more realistic heterogeneous model is developed instead of the conventional homogenous modelling approach to simulate the phase change phenomenon of the Nano-enhanced phase change material (NEPCM). The presence of the nanoadditives in PCM have a substantial effect on the heat transfer and fluid flow characteristics as well as on the phase change morphology. Thermal field, velocity field, nanoadditive concentration field and solidified fraction field predictions are discussed. The effects of nanoaddtive entrapment, ejection and mobility across the mushy zone with Brownian and thermophores diffusions are delineated.