One of the renewable technologies that trigger the dissemination of sustainable development in the power sector is Concentrated Solar Power (CSP). Within the so-called Gas-Phase Receiver Pathway, the Gas-Phase (GP) receivers use gaseous Heat-Transfer Fluid (HTF), to transfer energy, either through a direct or indirect coupling, to and from a thermal storage unit. Inside the receiver, the HTF typically passes through relatively small flow channels and is heated to temperatures, which should guarantee the target of 700°C for&nbsp;sCO2 in the secondary loop. One key point for that technology is then the design of receivers with enhanced heat transfer to the HTF. Such a promotion could be obtained by increasing the turbulence in the pipes using a suitable turbulence promoter or by increasing the heat transfer surface with the insert of porous media.In this work, a porous medium constituted by a packed bed of Raschig Rings is simulated to evaluate its effect on the heat transfer enhancement of the fluid. Although the Raschig Rings are frequently used in fixed bed catalytic reactors in chemical industries where highly exothermic reactions should be handled, their employment for CSP applications has been proposed recently. In this regard, a planar receiver mock-up equipped with copper Raschig Rings, and brazed together to form a porous metal matrix, has been tested in 2019 at the Plataforma Solar de Almeria, and the results allowed computing a promising Performance Evaluation Criteria with respect to the plain receiver [1]. The experimental results also promised confidence in the numerical tools developed to analyse the flow and temperature regions inside the Rings bed. Based on those results, in this research, a tubular topology of a receiver equipped with the Rings is investigated numerically, aiming at analysing in detail the mechanisms of the heat transfer from the wall to the HHF through the porous metal matrix in symmetric and asymmetric heating conditions. The computed results are compared to available correlations [2] to verify their suitability for the case at hand. The investigation carried out in this work represents a first step in the optimization of the porous medium structure inside the tubular receiver.&nbsp;[1] L. Savoldi, A. Allio, A. Bonvento, M. Cantone, J. Fernandez Reche, Experimental and numerical investigation of a porous receiver equipped with Raschig Rings for CSP applications,Solar Energy, 212, 2020, pp. 309-325.[2] M. David, A. Toutant, F. Bataille, Numerical development of heat transfer correlation in asymmetrically heated turbulent channel flow, International Journal of Heat and Mass Transfer, 164, 2021, 120599.

First Numerical Evaluation of the Thermal Performance of a Tubular Receiver Equipped With Raschig Rings for CSP Applications

Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2021/volume/85109

ASME 2021 Power Conference (POWER2021)

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