Study on the flow and heat transfer characteristics of hitec salt in solar vacuum collector tube

Abstract

ABSTRACT With the continuous development of parabolic trough collectors technology, molten salt has gradually become a popular heat transfer fluid used in solar vacuum collector tubes. An experimental platform with Hitec salt (7% NaNO3, 53% KNO3, and 40% NaNO2) circulation loop was established to study the convective heat transfer characteristics of the molten salt side in the solar vacuum collector tube, and the convective heat transfer experiments were carried out under different irradiation intensities. The results show that increased irradiation intensity can effectively enhance the convection heat transfer. The experimental data under 0W/m2 have a significant deviation from the Nusselt number junction calculated by the classical heat transfer equations, and the deviation ranges from −7.9% to + 15.2%. The heat transfer equations under 0W/m2 and 850W/m2 were fitted, and the deviations between the experimental data and the calculated results of the fitted equations were −8% to + 8% and −9.9% to + 9.5%, respectively. A high-precision fitting strategy based on a neural network algorithm was introduced, the maximum deviation was −3.18% to + 3.35% and −3.9% to + 3.8%, which shows better fitting effect. This study can provide fundamental heat transfer data for the flow heat transfer of ternary molten salt in solar vacuum collector tubes, and provide theoretical guidance for the distribution of heat collection field in trough solar photovoltaic power station.