Multi-objective optimization of a solar receiver considering both the dimple/protrusion depth and delta-winglet vortex generators

Abstract

In this study, multi-objective optimization of the performance of a solar receiver with dimple and delta-winglet vortex generators (DWVGs) is carried out. The thermal performance and outlet dimensionless turbulent kinetic energy (TKE) are chosen as the optimization objectives. The dimple depth, dimple arrangement, the length, height, angle and spacing of the DWVGs are selected as the optimization variables. The Non-Dominated Sorting Genetic Algorithm II (NSGA II) optimization algorithm and computational fluid dynamics (CFD) are adopted. The Re number is fixed as 15,000 in the optimization process. After the optimization, five cases including a Baseline are studied in detail. Results of the Pareto front, flow structure, heat transfer, TKE and thermal performance are included. The results show that the Pareto front is obtained by using this optimization platform. The mixing and thermal performance are significantly increased in the optimal cases. In addition, the solar receiver with inline arranged dimples and DWVGs provides better performance of both mixing and heat transfer than the stagger arrangement. The flow impingement on the protrusion leading edge and half downstream the dimple, the reattachment downstream the dimple are responsible for the thermal performance augmentation while the vortices generated by dimples and protrusions contribute to the increase of mixing. As a result, the heat transfer is enhanced by 75.78%, the friction factor is increased by 166.57% and the TKE is augmented by 5.2 times, respectively. The thermal performance analysis indicates that optimization increases the thermal performance by 72%.