Analysis of the direct steam generation, thermal stresses, and deformations in a tubular receiver of a solar tower

In solar tower systems, the thermal receiver is a crucial element. Solar receivers may be exposed to high non-uniform heat fluxes, which requires consideration during their structural design. This paper presents a numerical study of the direct steam generation, thermal stress, and total deformations on a representative tube of an external solar receiver. A non-uniform distribution of solar heat flux on the receiver was considered. The sub-cooled boiling and the direct steam generation were analyzed in terms of the temperature field, the volumetric vapor fraction distribution, and steam quality. Under this configuration, the system can produce a steam quality of 0.113%. To develop the structural analysis of the tube, the internal and external temperature fields of its walls were introduced as boundary conditions. Numerical methodologies for direct steam generation, temperatures, and deformation were validated with experimental data. Since the base case presented high deformation (78.63 cm), the use of clips was proposed. Besides, the number, size, and location of the clips were tested. It was found that deformation can be reduced by about 99.1% by placing clips at different positions along the tube. However, the von-Mises stresses increased, but they did not reach the ultimate tensile strength.