Nitrate salt phase transition study for molten salt loop working fluid consideration

Molten salt is an essential topic to study as a working fluid in circulation loop trials. Experimental and computational studies were presented to analyse the phase transition of nitrate salts and provide parameters that could support the consideration of the working fluid in molten salt loop testing. The NaNO 3 salt, KNO 3 salt, and the eutectic mixture of both were studied in the present work. The salt phase transition was studied in an apparatus built following the molten salt loop heater section. The apparatus was constructed by winding nichrome wire around a stainless steel pipe 2.667 cm in diameter and 20 cm long. The nichrome wire was connected to an adjustable AC voltage regulator to obtain variations in heating power in the experiment. The data acquisition integrated K-type thermocouple was used to acquire temperature change data in the centre of the apparatus. The conventional and thermal cameras were used to support the visual observation of the top surface of the apparatus. Modelling was conducted with the help of ANSYS Fluent software based on input from experimental results. At the same power, the difference in efficiency between the eutectic salt and KNO 3 salt reached 72.2%, while with NaNO 3 salt, it reached 97.7%. The results showed that the low melting temperature and the low latent heat are crucial characteristics of salt as a working fluid consideration for efficient heating in the molten salt loop.