Effect of Tube Size on the Thermal Stress in Concentrating Solar Receiver Tubes

Abstract

High-level thermal stress in the receiver tubes is detrimental for the integrity and safety of concentrating solar power (CSP) plants and is a major concern in CSP design. One important factor affecting the thermal stress is the tube size. However, conventional CSP designs mainly focus on heat transfer efficiency and pumping loss when considering the tube size effect. Investigations into the influence of tube wall thickness and diameter on the thermal stress profile are still lacking. In this paper, we bridge this knowledge gap by conducting a coupled fluid-thermal-structural simulation. The results demonstrate that the peak thermal stress correlates linearly with both the tube diameter and thickness. In comparison, the increase in thickness raises thermal stress more profoundly than the tube diameter does. Further analysis also reveals a shift in the axial thermal stress distribution by decreasing thickness or enlarging tube diameter. Notably, the axial stress on the tube front section's inner surface is inverted from tension to compression at small thicknesses or large diameters. This change is found to be attributed to the diminishing of the radial temperature gradient. These findings are beneficial in CSP receiver designs for mitigating the high-stress risks and extending its operational lifespan.