Numerical study and experimental validation of the effects of orientation and configuration on melting in a latent heat thermal storage unit

Enhancing the effectiveness of solar power, including daytime storage for overnight use, is essential to reduce fossil fuel usage. This work explores the melting behaviour of paraffin wax in shell and tube latent heat thermal storage unit (LHSU) in different configurations and orientations. Numerical simulation were carried out and compared with experimental measurements for non-finned and finned configurations arranged vertically during the melting (charging) process. A commercial paraffin wax was used as a phase change material (PCM). The temperature and liquid fraction of the PCM during the course of the melting process in both configurations were used for model validation. When considering the liquid fraction, the numerical results showed excellent qualitative agreement with the experimental images for all the cases being studied. Specifically, the shape and progress of the melting front showed good agreement between the experiments and numerical results. Furthermore, the model predicted well the experimentally measured temperature in the melting PCM, with a maximum average discrepancy of 3.6%. The validated model was then used to investigate different process configurations. The results indicated that the addition of fins enhanced the melting process by an average of 50%. The non-finned tubes had a superior melting rate in the horizontal orientation over the vertical orientation, while orientation was found to have only a minor impact on the melting process with finned tubes.