Concentrated Solar Power (CSP) with Thermal Energy Storage (TES) has the potential to realize grid parity. This can be achieved by operating CSP systems at temperatures above 700 °C to reach high thermal efficiencies (> 50%). However, operating CSP systems at elevated temperatures poses several problems, among which the design of solar receivers to handle increased thermal loads is critical. To this end, this work explores and optimizes various swirl-inducing internal fin designs for improving heat transfer in solar receiver tubes. These fin designs, in addition to enhancing the thermal performance of receiver tubes, are also capable of reducing temperature unevenness caused by nonuniform solar loads. This work optimizes the geometric parameters such as height and helical pitch of these fin designs by maximizing the Nusselt number with a constraint on the friction factor. The fin design optimization, however, is computationally intensive, often requiring hundreds of simulation call to the Computational Fluid Dynamics (CFD) model. To circumvent this problem, this work employs surrogate models to approximate the simulation outputs needed during the optimization.