Computational Fluid Dynamics Analysis of Absorber Tube with Molten Salt-based Nanofluids and Porous Medium Inserts

In the field of solar applications, the performance of the system is significantly influenced by the design of the absorber tube, including the composition of heat transfer fluids within it and its geometric configuration. This study presents a computational fluid dynamics (CFD) model that combines molten salt-based nanofluids with porous medium inserts within the absorber tube. Two distinct configurations of porous inserts are investigated: one attached to the tube wall, referred to as 'enhanced tube 1 (ET1),' and the other integrated into the core zone, denoted as 'enhanced tube 2 (ET2).' This research explores how the thickness of the porous medium in these two configurations impacts the thermal and hydraulic performance of the absorber tube when used with molten salt-based nanofluids. Parameters considered include flow and heat transfer characteristics, as well as a performance evaluation criterion. The thickness of the porous medium is found to play an essential role in the thermo-hydraulic performance of the receiver tube. Across all sizes of ET1, significantly better heat transfer performance is consistently observed when compared to all ET2 configurations. It is important to note that the introduction of porous inserts does result in an increase in pressure drop, which varies with the thickness of the inserts in both ET1 and ET2 configurations. Consequently, when evaluating the overall thermo-hydraulic performance, the ranking stands as ET1 > smooth tube > ET2. Additionally, the performance evaluation criterion of ET1 exhibits an initial increase, followed by a subsequent decrease as the thickness of the porous inserts varies. This pattern suggests the presence of an optimal thickness, with a radius of 0.1, that maximizes performance. This study might contribute to the performance improvement of the absorber tube used in solar applications.