Evaluation of the scraping forces in active latent heat thermal energy storages

Kurzfassung

Low-cost Phase Change Materials (PCM) usually have a low thermal conductivity. During the discharge process, solidified PCM on the heat transfer surface acts as a thermal insulator, resulting in a reduction of the heat transfer between the PCM and the heat transfer fluid, thus the discharge power is reduced as the PCM solidifies. In active latent heat thermal energy storages (ALHTES), the solidified PCM layer is mechanically removed from the heat transfer surface by a scraper to maximize the heat transfer. In this study, this parasitic mechanical energy is quantified experimentally for the first time to optimize the design of future ALHTES. The required scraping force is measured for decanoic acid and paraffin, resulting in a value between 150 and 350 N*m-1 depending on the angle of the scraper.