Investigation of stress and deflection in absorber of parabolic trough solar collector for direct steam generation

Abstract

The tubular absorber of a parabolic trough solar collector (PTSC) experiences deflection and thermal stress during the operation due to the adverse circumferential and longitudinal thermal gradient in the direct steam generation (DSG) process. This study presents the coupled three-dimensional thermal–structural analysis of the absorber tube by combining heat transfer and static structural analyses using ANSYS Fluent 2021R1 software. The receiver of the LS-3 solar collector unit with a length of 4.06 m is considered as a computational domain with mass flow rates of 0.4 kg/s and 0.6 kg/s, an operating pressure of 100 bar, and the direct normal irradiance (DNI) of 750 W/m2. The deformation and stress analyses have been performed for preheating, evaporation, and superheating stages of the DSG process at solar noon. Under the subjected boundary conditions, the circumferential thermal gradient at the middle of the absorber in preheating, evaporation, and superheating sections are 27 K, 13 K, and 31 K, respectively. The maximum and minimum deflections observed in the absorber tube are 17.6 mm and 7.6 mm, respectively. The maximum and minimum normal stress along the axial direction on top of the absorber are 26.0 MPa and 12.6 MPa, respectively. It is observed that normal stresses along the axial direction is maximum at the mid of the absorber. The maximum thermal strains observed in preheating, evaporation, and superheating sections are 4.6 mm/m, 5.2 mm/m, and 5.6 mm/m, respectively.