Influence of longitudinal clips in thermal stresses and deflection in solar tubular receivers

Abstract Mechanical boundary conditions in tubular receivers of solar power tower plants have a main role in the thermal stress distribution and tube deflection. Longitudinal supports, particularly, has an strong influence on stress and displacements, since they prevent the tube bending. In this work, the influence of longitudinal supports, on tube deflection and stress has been studied in external-cylindrical receivers, using an analytical methodology, which it is able to take into account the tube geometry in the deflection calculation. Therefore, real tube geometry with elbows can be considered. Results for two aiming strategies, one equatorial and another that flattens the heat flux, have been compared for different clips distances, from 1 to 9 meters. The analytical methodology developed in Matlab provides lower computational cost than the numerical model developed in Abaqus. Results show that clip distribution has a significant impact on thermal stress. For clips distance of 2 meters or lower, the generalised plane strain solution provides the stress distribution along the tube accurately, with a tube deflection lower than 1 millimetrer. When clips distance increases, the longitudinal stress distribution differs from the plane strain case, and the deflection increases to non-desirable values. Deflection is greater at tube ends, and aiming strategies that flatten the heat flux increases the displacement in that regions.