Abstract: Based on the single tube model of the receiver, the temperature drop characteristics of the endothermic tube such as the heat flux, molten salt flow rate and surface convection heat transfer coefficient were studied through numerical simulations on the scenarios under cloud occlusion before and after protection schemes implemented. The results exhibit limited impacts of radiation heat flux density on the elapsed time for temperature at the molten salt outlet to decrease to close to the solidification point. Moreover, the greater the convection heat transfer coefficient, the more likely the molten salt solidification may appear; while the lower the molten salt inlet velocity, the longer time it will take for the molten salt outlet temperature to drop close to the solidification point. Without the protective device, the time taken to reach the freezing temperature of the molten salt at the outlet is about 20 seconds. The scheme of adding the protective device and reducing the inlet velocity of molten salt can be applied to extend the time by almost six times, or as much as 130 seconds. Thereby system security can be greatly improved.

Key words: absorber tube, molten salt, temperature drop characteristic, cloud occlusion