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

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.

KEYWORDS:

• Molten salt
• solar vacuum collector tube
• solar irradiation
• convective heat transfer
• neural network

Acknowledgements

This work was supported by Jiangsu Postgraduate Research and Practice Innovation Program (Grant No. SJCX23_1578). The authors appreciate the solar vacuum collector tube provided by Royal Tech CSP Limited company for this test.

Disclosure statement

This study received funding from Jiangsu Postgraduate Research and Practice Innovation Program and Royal Tech CSP Limited company. The funders were not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication. All authors declare no other competing interests.

Additional information

Funding

This work was supported by Jiangsu Postgraduate Research and Practice Innovation Program [Grant No. SJCX23_1578].

Notes on contributors

Guojian Ji

Guojian Ji is an associate professor and master supervisor of Changzhou University. His main research interests are waste heat recovery and flow heat transfer.

Zhi Chen

Zhi Chen is a master’s candidate at Changzhou University. His research interests are flow heat transfer.

Yicheng Chu

Yicheng Chu is a master’s candidate at Changzhou University. His research interest is flow and phase-transition heat.

Qunfeng Zou

Qunfeng Zou is a lecturer and master tutor at Changzhou University. His main research interest is flow-induced vibration and heat transfer.

Beibei Lu

Beibei Lu is a lecturer at Changzhou University. Her research interests are boiler principles and waste heat recovery.

Xiaoqing Zhou

Xiaoqing Zhou is a master’s candidate at Changzhou University. His research interests are gas adsorption.