Optimization of the overall thermal performance in gradient-packed bed receivers

A uniform gradient-packed bed receiver (U-GPBR) is proposed, consisting of uniform quartz glass balls in the front layer and ceramic balls in the rear layers, to enhance the penetration depth of solar radiation and improve thermal efficiency. Additionally, a non-uniform gradient-packed bed receiver (N-GPBR) equipped with non-uniform quartz glass and ceramic balls is introduced to address the trade-off between thermal efficiency and pressure drop. The optimal arrangement of the N-GPBR is determined using the orthogonal optimization method. The heat transfer processes of both the U-GPBR and N-GPBR, particularly the forward problem, are investigated using a particle-scale method, along with experimental validation. Results indicate that smaller particles of U-GPBR achieve greater thermal efficiency but incur a higher unit pressure drop. A higher working temperature necessitates that the U-GPBR add additional layers of glass balls. Through orthogonal optimization and entropy evaluation, the optimal case, G75B75, achieves the best comprehensive score of 0.83 along with the highest thermal efficiency at 83.4 %. The optimized GPBR design introduces a novel method for obtaining high-temperature solar receivers for advanced power cycles.