Thermo-hydraulic design and economical manufacturing assessment of bayonet central receivers for solar power towers

This study presents a set of novel initial design strategies for sizing bayonet tubes applied to solar external receivers. The initial design strategies considered key variables that affect the performance of bayonet tubes, such as fluid velocity, pressure drop, and convection coefficients. A numerical simplified model was developed to assess these design strategies, excluding layouts that did not enhance convective heat transfer or exhibited much larger pressure drops than simple tubes. Computational Fluid Dynamics (CFD) simulations were conducted to improve the understanding of the bayonet tube behavior and to verify the appropriateness of the simplified initial design model and its assumptions. According to the obtained results, concentric bayonet tube layouts sized with these strategies lead to higher convection coefficient ratios than simple tubes at the cost of increasing the pressure drop, resulting in Performance Evaluation Criterion (PEC) values below 1. Nevertheless, when these layouts are reconfigured eccentrically, they show a larger convection heat transfer efficiency, a reduced pressure drop, and a lower maximum temperature compared to those of a simple tube. Some bayonet tube designs may be acceptable from a thermomechanical perspective, but they may not be economically viable. Hence, the manufacturing costs of both bayonet and conventional receivers were estimated. Besides, using 316H steel for the interior bayonet tube while retaining Haynes 230 for the exterior tube, to withstand the concentrated solar radiation, can reduce the receiver cost by up to 13% compared to a simple tube receiver.