Experimental study on thermal performance of a mobilized thermal energy storage system: A case study of hydrated salt latent heat storage

A mobilized thermal energy storage (M-TES) system was proposed to utilize the renewable energy or recover the industrial waste heat in this paper. The M-TES system with 215 kg sodium acetate trihydrate as phase change material (PCM) filled into a tube-in-tank heat exchanger was designed and experimental tests were conducted to evaluate its thermal performance. The charging-discharging behavior of M-TES system was observed and temperature evolutions of PCM and heat transfer fluid (HTF) were monitored. The charging process of the M-TES system could be accomplished in 1200 s; while for energy discharging process, it took a little longer (1400 s) due to the prevention of natural convection. It also revealed that the non-uniform temperature distribution of PCM would result in asynchrony of melting/solidification. The PCM in the middle part of the tubes would melt at first, whereas the temperature of the PCM close to the end of the tubes increased much slower. The temperature difference was much more significant during the discharging process. Super cooling could be found easily for the PCM in the ends of tubes. The released heat in the discharging process was applied to heat the cooling water to mimic the domestic consumption of hot water to investigate the thermal performance of energy discharging. With perfect performance of our indirect contact heat exchanger, the thermal efficiency was estimated of 79.4%. Our tests would provide an experimental basis for the application of the low-temperature mobilized LHTES system. (C) 2019 Elsevier B.V. All rights reserved.