Experimental and numerical study on cold-start safety of a kilowatt-scale chloride salt receiver prototype for the next-generation solar power tower

During cold-start, the lack of effective convective heat transfer inside a high-temperature chloride salt receiver may cause a rapid wall-temperature rise and large circumferential temperature gradients within a short period, resulting in local overheating and thermal stress concentration. These transient thermal loads pose a considerable stress-failure risk and therefore require effective safety regulation. To address the high risk of stress failure, a cold-start safety regulation experimental platform for the high temperature chloride salt receiver was constructed, and a three-dimensional transient thermal-mechanical analysis model was established for a kilowatt-scale receiver prototype. The variations in temperature and thermal stress of the prototype were investigated, and an illuminated-side wall stepwise preheating strategy was proposed. Subsequently, a back-side heating strategy was developed based on an inverse heat conduction problem model, with the ideal circumferential temperature difference and stress safety factor as optimization objectives. The two strategies were further combined for coordinated regulation of the cold-start safety. Results show that the average relative deviations between the experimental and simulated temperatures of the four receiver tubes are 2.22%, 3.16%, 3.82%, and 3.39%, respectively. Compared with simultaneous activation of all xenon lamps, stepwise preheating reduces the peak values of circumferential temperature difference and equivalent stress by 26.94%–42.62% and 26.17%–44.46%, respectively. With the additional back-side heating strategy, these two indicators are further reduced by 10.63%–41.88% and 8.94%–41.47%, respectively. The minimum safety factors reach 1.21–2.88, demonstrating that the combined preheating strategy can effectively improve the cold-start safety of high-temperature chloride salt receivers.